U.S. patent number 8,118,870 [Application Number 11/134,067] was granted by the patent office on 2012-02-21 for expandable articulating intervertebral implant with spacer.
This patent grant is currently assigned to Flexuspine, Inc.. Invention is credited to Charles R. Gordon, Heather S. Hanson, Corey T. Harbold.
United States Patent |
8,118,870 |
Gordon , et al. |
February 21, 2012 |
Expandable articulating intervertebral implant with spacer
Abstract
An expandable articulating intervertebral implant is described
for insertion between vertebrae of a human spine. The expandable
intervertebral implant includes an upper body that engages a first
vertebra of the human spine, a lower body that engages a second
vertebra of the human spine, and an insert. The upper body may
include an upper portion and a lower portion. The insert may be
positioned between an inferior surface of the lower portion of the
upper body and a superior surface of the lower body. The insert may
be translated or rotated to increase a separation distance between
the lower body and the upper body. A spacer may be inserted between
the upper body and the lower body to maintain at least a portion of
the increased separation distance between the upper body and the
lower body after expansion of the intervertebral implant in the
human spine.
Inventors: |
Gordon; Charles R. (Tyler,
TX), Harbold; Corey T. (Tyler, TX), Hanson; Heather
S. (San Antonio, TX) |
Assignee: |
Flexuspine, Inc. (Pittsburgh,
PA)
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Family
ID: |
35462166 |
Appl.
No.: |
11/134,067 |
Filed: |
May 20, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050273174 A1 |
Dec 8, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11050632 |
Feb 3, 2005 |
7753958 |
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10634950 |
Aug 5, 2003 |
7204853 |
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10660155 |
Sep 11, 2003 |
7316714 |
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10777411 |
Feb 12, 2004 |
7909869 |
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PCT/US2004/025090 |
Aug 4, 2004 |
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10634950 |
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10634950 |
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Current U.S.
Class: |
623/17.16;
623/17.15 |
Current CPC
Class: |
A61F
2/4425 (20130101); A61B 17/7008 (20130101); A61B
17/7032 (20130101); A61F 2/4405 (20130101); A61B
17/7007 (20130101); A61F 2/4455 (20130101); A61F
2/4611 (20130101); A61B 17/701 (20130101); A61B
17/7023 (20130101); A61B 17/7005 (20130101); A61F
2002/443 (20130101); A61F 2/30767 (20130101); A61F
2002/30131 (20130101); A61F 2002/3052 (20130101); A61F
2220/0033 (20130101); A61F 2230/0015 (20130101); A61F
2002/30462 (20130101); A61F 2002/3079 (20130101); A61F
2002/30225 (20130101); A61F 2002/30383 (20130101); A61F
2002/30471 (20130101); A61F 2002/30515 (20130101); A61F
2002/30624 (20130101); A61B 17/7064 (20130101); A61F
2002/30579 (20130101); A61F 2220/0075 (20130101); A61F
2220/0025 (20130101); A61B 17/7037 (20130101); A61F
2002/305 (20130101); A61F 2002/30492 (20130101); A61F
2002/4629 (20130101); A61F 2310/00023 (20130101); A61B
17/86 (20130101); A61F 2002/4628 (20130101); A61F
2002/30601 (20130101); A61F 2002/30772 (20130101); A61F
2230/0069 (20130101); A61F 2250/0006 (20130101); A61F
2002/30235 (20130101); A61F 2002/30505 (20130101); A61F
2002/30841 (20130101); A61F 2002/30904 (20130101); A61F
2230/0013 (20130101); A61F 2002/30538 (20130101); A61F
2002/3055 (20130101); A61F 2220/0091 (20130101); A61F
2002/3023 (20130101); A61F 2210/0014 (20130101); A61F
2002/30507 (20130101); A61F 2002/30578 (20130101); A61B
17/80 (20130101); A61F 2002/30476 (20130101); A61F
2002/30556 (20130101); A61F 2002/30369 (20130101); A61F
2002/30649 (20130101); A61F 2002/4622 (20130101); A61F
2250/0009 (20130101); A61F 2002/2835 (20130101); A61F
2002/30331 (20130101); A61F 2002/30365 (20130101); A61F
2002/30563 (20130101); A61F 2002/30662 (20130101); A61F
2002/30785 (20130101); A61F 2002/4627 (20130101); A61F
2002/30133 (20130101); A61F 2002/30565 (20130101); A61F
2002/30092 (20130101) |
Current International
Class: |
A61F
2/44 (20060101) |
Field of
Search: |
;623/17.16,17.15 |
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|
Primary Examiner: Sweet; Thomas J
Assistant Examiner: Prone; Christopher D
Attorney, Agent or Firm: Meyertons, Hood, Kivlin, Kowert
& Goetzel, P.C. Meyertons; Eric B.
Parent Case Text
PRIORITY
This application is a continuation of U.S. patent application Ser.
No. 11/050,632 entitled "Functional Spinal Units" to Charles R.
Gordon, Corey T. Harbold, and Heather S. Hanson, filed on Feb. 3,
2005 now U.S. Pat. No. 7,753,958. U.S. patent application Ser. No.
11/050,632 is a continuation in part of U.S. patent application
Ser. No. 10/634,950 now U.S. Pat. No. 7,204,853; U.S. patent
application Ser. No. 10/660,155 now U.S. Pat. No. 7,316,714; U.S.
patent application Ser. No. 10/777,411 now U.S. Pat. No. 7,909,869;
and PCT Application No. US2004/025090. PCT Application
US2004/025090 entitled "Artificial Spinal Unit Assemblies" to
Charles Gordon and Corey Harbold, filed on Aug. 4, 2004, claims the
benefit of U.S. patent application Ser. No. 10/634,950; U.S. patent
application Ser. No. 10/660,155; and U.S. patent application Ser.
No. 10/777,411. U.S. patent application Ser. No. 10/777,411
entitled "Artificial Spinal Unit Assemblies" to Charles Gordon and
Corey Harbold, filed on Feb. 12, 2004, is a continuation in part of
U.S. patent application Ser. No. 10/634,950. U.S. patent
application Ser. No. 10/660,155 entitled "Artificial Functional
Spinal Unit Assemblies" to Charles Gordon and Corey Harbold, filed
on Sep. 11, 2003, is a continuation in part of U.S. patent
application Ser. No. 10/634,950. U.S. patent application Ser. No.
10/634,950 entitled "Artificial Functional Spinal Unit Assemblies"
to Charles Gordon and Corey Harbold was filed on Aug. 5, 2003.
Claims
What is claimed is:
1. An intervertebral implant for a human spine, comprising: an
upper body comprising a superior surface and an inferior surface
wherein the superior surface of the upper body is configured to
engage a first vertebra of the human spine; a lower body comprising
a superior surface and an inferior surface, wherein the inferior
surface of the lower body is configured to engage a second vertebra
of the human spine; an insert configured to be positioned between
the superior surface of the lower body and the inferior surface of
the upper body before insertion of the intervertebral implant
between the first vertebra and the second vertebra of the human
spine, wherein the insert comprises a recess, wherein the insert is
configured such that translation or rotation of the insert
increases a separation distance between the upper body and the
lower body; and a spacer configured to be inserted between the
lower body and the upper body to maintain at least a portion of the
increased separation distance between the upper body and the lower
body, wherein the spacer comprises: a substantially planar inferior
surface; a lip extending from an edge of the substantially planar
inferior surface of the spacer, wherein the lip is configured to
engage a complementary surface of the lower body when the insert is
inserted between the lower body and the upper body to facilitate
insertion or retention of the spacer during use; and a protrusion
extending from the substantially planar inferior surface of the
spacer, wherein the protrusion of the spacer is configured to
substantially mate with the recess of the insert to inhibit
unintentional removal of the spacer from the intervertebral implant
during use.
2. The intervertebral implant of claim 1, wherein the spacer is
further configured to be press fit between the lower body and the
upper body.
3. The intervertebral implant of claim 1, wherein the spacer is
further configured to be loose fit between the lower body and the
lower portion of the upper body.
4. The intervertebral implant of claim 1, wherein the spacer is
further configured to be reversibly locked in place between the
lower body and the lower portion of the upper body.
5. The intervertebral implant of claim 1, wherein the spacer is
further configured to be irreversibly locked in place between the
lower body and the upper body.
6. The intervertebral implant of claim 1, wherein the lower body
further comprises a lip configured to facilitate insertion or
retention of the spacer in the intervertebral implant.
7. The intervertebral implant of claim 1, wherein the lip extends
around substantially all outward facing portions of an external
edge of the inferior surface of the spacer.
8. The intervertebral implant of claim 1, wherein the lip extends
around three of four sides of an external edge of the substantially
planar superior or inferior surface of the spacer.
9. An intervertebral implant for a human spine, comprising: an
upper body comprising a superior surface and an inferior surface,
wherein the superior surface of the upper body is configured to
engage a first vertebra of the human spine; a lower body comprising
a superior surface and an inferior surface, wherein the inferior
surface of the lower body is configured to engage a second vertebra
of the human spine; an insert configured to be positioned between
the superior surface of the lower body and the inferior surface of
the upper body such that the upper body contacts the lower body
before insertion of the intervertebral implant between the first
vertebra and the second vertebra of the human spine, wherein the
insert comprises a longitudinal axis extending between a first end
and a second end of the insert, wherein the insert is configured to
be rotated about the longitudinal axis such that at least one of
the first end and the second engages at least one of the upper body
and the lower body to increase a separation distance between the
upper body and the lower body after insertion of the intervertebral
implant between the first vertebra and the second vertebra of the
human spine; and a spacer configured to be inserted between the
lower body and the upper body to maintain at least a portion of the
increased height of the intervertebral implant, wherein the spacer
comprises a lip extending about an edge of a substantially planar
superior surface or a substantially planar inferior surface of the
spacer, wherein the lip extends substantially perpendicular to the
substantially planar superior surface or the substantially planar
inferior surface, and wherein the lip is configured to engage a
complementary portion of at least one of the upper body and the
lower body to guide insertion or facilitate retention of the spacer
between the upper body and the lower body.
10. The intervertebral implant of claim 9, wherein the spacer is
further configured to be press fit between the lower body and the
upper body.
11. The intervertebral implant of claim 9, wherein the spacer is
further configured to be loose fit between the lower body and the
lower portion of the upper body.
12. The intervertebral implant of claim 9, wherein the spacer is
further configured to be reversibly locked in place between the
lower body and the lower portion of the upper body.
13. The intervertebral implant of claim 9, wherein the spacer is
further configured to be irreversibly locked in place between the
lower body and the upper body.
14. The intervertebral implant of claim 9, wherein the upper body
further comprises a lip configured to facilitate insertion or
retention of the spacer in the intervertebral implant.
15. The intervertebral implant of claim 9, wherein the lower body
further comprises a lip configured to facilitate insertion or
retention of the spacer in the intervertebral implant.
16. The intervertebral implant of claim 9, wherein the lip extends
around substantially all outward facing portions of an external
edge of the substantially planar superior surface or the
substantially planar inferior surface of the spacer.
17. The intervertebral implant of claim 9, wherein the lip extends
around three of four sides of an external edge of the substantially
planar superior surface or the substantially planar inferior
surface of the spacer.
18. The intervertebral implant of claim 9, wherein the spacer
comprises a protrusion extending outward from the substantially
planar inferior surface of the spacer, wherein the protrusion is
configured to substantially mate with a complementary recess of the
intervertebral implant to inhibit unintentional removal of the
spacer from the intervertebral implant during use.
19. The intervertebral implant of claim 18, wherein the
complementary recess comprises a recess on the insert.
20. An intervertebral implant for a human spine, comprising: an
upper body comprising a superior surface and an inferior surface,
wherein the superior surface of the upper body is configured to
engage a first vertebra of the human spine; a lower body comprising
a superior surface and an inferior surface, wherein the inferior
surface of the lower body is configured to engage a second vertebra
of the human spine; an insert configured to be positioned between
the superior surface of the lower body and the inferior surface of
the upper body before insertion of the intervertebral implant
between the first vertebra and the second vertebra of the human
spine, wherein the insert is configured such that translation or
rotation of the insert increases a height of the intervertebral
implant to expand the intervertebral implant; and a spacer
configured to be inserted between the lower body and the upper body
to maintain at least a portion of the increased height of the
intervertebral implant, wherein at least a portion of an external
edge of a superior surface or an inferior surface of the spacer
comprises a lip extending from the superior surface or the inferior
surface of the spacer, wherein the lip is configured to engage a
complementary portion of the upper body or lower body to facilitate
insertion or retention of the spacer between the lower body and the
upper body.
21. The intervertebral implant of claim 20, wherein the spacer is
further configured to be press fit between the lower body and the
upper body.
22. The intervertebral implant of claim 20, wherein the spacer is
further configured to be loose fit between the lower body and the
lower portion of the upper body.
23. The intervertebral implant of claim 20, wherein the spacer is
further configured to be reversibly locked in place between the
lower body and the lower portion of the upper body.
24. The intervertebral implant of claim 20, wherein the spacer is
further configured to be irreversibly locked in place between the
lower body and the upper body.
25. The intervertebral implant of claim 20, wherein the upper body
further comprises a lip configured to facilitate insertion or
retention of the spacer in the intervertebral implant.
26. The intervertebral implant of claim 20, wherein the lower body
further comprises a lip configured to facilitate insertion or
retention of the spacer in the intervertebral implant.
27. The intervertebral implant of claim 20, wherein the lip extends
around substantially all outward facing portions of an external
edge of the superior surface or the inferior surface of the
spacer.
28. The intervertebral implant of claim 20, wherein the lip extends
around three of four sides of an external edge of the superior
surface or the inferior surface of the spacer.
29. The intervertebral implant of claim 20, wherein the spacer
comprises a protrusion extending outward from the inferior surface
of the spacer, wherein the protrusion is configured to
substantially mate with a complementary recess of the
intervertebral implant to inhibit unintentional removal of the
spacer from the intervertebral implant during use.
30. The intervertebral implant of claim 29, wherein the
complementary recess comprises a recess on the insert.
31. An intervertebral implant for a human spine, comprising: an
upper body comprising an inferior surface and a superior surface,
wherein the superior surface of the upper body is configured to
engage a first vertebra of the human spine; a lower body comprising
a superior surface and an inferior surface, wherein the inferior
surface of the lower body is configured to engage a second vertebra
of the human spine; and an expansion device configured to increase
a separation distance between the upper body and the lower body to
from a gap between the inferior surface of the upper body and the
superior surface of the lower body, and a spacer configured to be
inserted into the gap to maintain at least a portion of the
increased separation distance between the upper body and the lower
body, wherein the spacer comprises at least one of a substantially
planar inferior surface or a substantially planar superior surface,
wherein the substantially planar superior or inferior surface
comprises a lip extending about an edge of the substantially planar
superior or inferior surface, wherein the lip extends substantially
perpendicular from the substantially planar superior surface or the
substantially inferior surface, and wherein the lip is configured
to engage a complementary portion of at least one of the upper body
and the lower body to guide insertion or facilitate retention of
the spacer between the upper body and the lower body.
32. The intervertebral implant of claim 31, wherein the spacer
comprises a protrusion extending from the substantially planar
inferior surface of the spacer, wherein the protrusion of the
spacer is configured to substantially mate with a recess in a
superior surface of the expansion device to inhibit unintentional
removal of the spacer from the intervertebral implant during use.
Description
BACKGROUND
1. Field of the Invention
Embodiments of the invention generally relate to functional spinal
implant assemblies for insertion into an intervertebral space
between adjacent vertebrae of a human spine, and reconstruction of
the posterior elements to provide stability, flexibility, and
proper biomechanical motion. More specifically, embodiments of the
invention relate to artificial functional spinal units including an
expandable artificial intervertebral implant that can be inserted
via a posterior surgical approach and used in conjunction with one
or more facet replacement devices to approach an anatomically
correct range of motion. Embodiments of the invention may also be
inserted via an anterior surgical approach.
2. Description of Related Art
The human spine is a complex mechanical structure including
alternating bony vertebrae and fibrocartilaginous discs that are
connected by strong ligaments and supported by musculature that
extends from the skull to the pelvis and provides axial support to
the body. The intervertebral discs provide mechanical cushion
between adjacent vertebral segments of the spinal column and
generally include three basic components: the nucleus pulposus, the
annulus fibrosis, and two vertebral end plates. The end plates are
made of thin cartilage overlying a thin layer of hard cortical bone
that attaches to the spongy, cancellous bone of the vertebral body.
The annulus fibrosis forms the disc's perimeter and is a tough
outer ring that binds adjacent vertebrae together. The vertebrae
generally include a vertebral foramen bounded by the anterior
vertebral body and the neural arch, which consists of two pedicles
and two laminae that are united posteriorly. The spinous and
transverse processes protrude from the neural arch. The superior
and inferior articular facets lie at the root of the transverse
process.
The human spine is a highly flexible structure capable of a high
degree of curvature and twist in nearly every direction. However,
genetic or developmental irregularities, trauma, chronic stress,
and degenerative wear can result in spinal pathologies for which
surgical intervention may be necessary. In cases of deterioration,
disease, or injury, a spinal disc may be removed from a human
spine. A disc may become damaged or diseased, reducing
intervertebral separation. Reduction of the intervertebral
separation may reduce a height of the disc nucleus, which may cause
the annulus to buckle in areas where the laminated plies are
loosely bonded. As the overlapping laminated plies of the annulus
begin to buckle and separate, circumferential or radial annular
tears may occur. Such disruption to the natural intervertebral
separation may produce pain, which may be alleviated by removal of
the disc and maintenance of the natural separation distance. In
cases of chronic back pain resulting from a degenerated or
herniated disc, removal of the disc becomes medically
necessary.
In some cases, a damaged disc may be replaced with a disc
prosthesis intended to duplicate the function of a natural spinal
disc. U.S. Pat. No. 4,863,477 to Monson, which is incorporated
herein by reference, discloses a resilient spinal disc prosthesis
intended to replace the resilience of a natural human spinal disc.
U.S. Pat. No. 5,192,326 to Bao et al., which is incorporated herein
by reference, describes a prosthetic nucleus for replacing just the
nucleus portion of a human spinal disc. U.S. Patent Application
Publication No. 2005/0021144 to Malberg et al., which is
incorporated herein by reference, describes an expandable spinal
implant.
In other cases, it may be desirable to fuse adjacent vertebrae of a
human spine together after removal of a disc. This procedure is
generally referred to as "intervertebral fusion" or "interbody
fusion." Intervertebral fusion has been accomplished with a variety
of techniques and instruments. It is generally known that the
strongest intervertebral fusion is the interbody fusion (between
the lumbar bodies), which may be augmented by a posterior or facet
fusion. In cases of intervertebral fusion, either structural bone
or an interbody fusion cage filled with bone graft material (e.g.,
morselized bone) is placed within the space where the spinal disc
once resided. Multiple cages or bony grafts may be used within that
space.
Cages of the prior art have been generally successful in promoting
fusion and approximating proper disc height. Cages inserted from
the posterior approach, however, are limited in size by the
interval between the nerve roots. Therefore, a fusion implant
assembly that could be expanded from within the intervertebral
space could reduce potential trauma to the nerve roots and yet
still allow restoration of disc space height. It should be noted,
however, that fusion limits overall flexibility of the spinal
column and artificially constrains the natural motion of the
patient. This constraint may cause collateral injury to the
patient's spine as additional stresses of motion, normally borne by
the now-fused joint, are transferred onto the nearby facet joints
and intervertebral discs. Thus, an implant assembly that mimics the
biomechanical action of the natural disc cartilage, thereby
permitting continued normal motion and stress distribution, would
be advantageous.
A challenge of instrumenting a disc posteriorly is that a device
large enough to contact the end plates and slightly expand the
space must be inserted through a limited space. This challenge is
often further heightened by the presence of posterior osteophytes,
which may cause "fish mouthing" of the posterior end plates and
result in very limited access to the disc. A further challenge in
degenerative disc spaces is the tendency of the disc space to
assume a lenticular shape, which requires a relatively larger
implant than often is easily introduced without causing trauma to
the nerve roots. The size of rigid devices that may safely be
introduced into the disc space is thereby limited.
The anterior approach poses significant challenges as well. Though
the surgeon may gain very wide access to the interbody space from
the anterior approach, this approach has its own set of
complications. The retroperitoneal approach usually requires the
assistance of a surgeon skilled in dealing with the visceral
contents and the great vessels, and the spine surgeon has extremely
limited access to the nerve roots. Complications of the anterior
approach that are approach-specific include retrograde ejaculation,
ureteral injury, and great vessel injury. Injury to the great
vessels may result in massive blood loss, postoperative venous
stasis, limb loss, and intraoperative death. The anterior approach
is more difficult in patients with significant obesity and may be
virtually impossible in the face of previous retroperitoneal
surgery.
Despite its difficulties, the anterior approach does allow for the
wide exposure needed to place a large device. In accessing the
spine anteriorly, one of the major structural ligaments, the
anterior longitudinal ligament, must be completely divided. A large
amount of anterior annulus must also be removed along with the
entire nucleus. Once these structures have been resected, the
vertebral bodies are over distracted in order to place the device
within the disc and restore disc space height. Failure to
adequately tension the posterior annulus and ligaments increases
the risk of device failure and migration. Yet in the process of
placing these devices, the ligaments are overstretched while the
devices are forced into the disc space under tension. This over
distraction can damage the ligaments and the nerve roots. The
anterior disc replacement devices currently available or in
clinical trials may be too large to be placed posteriorly, and may
require over distraction during insertion in order to allow the
ligaments to hold them in position.
SUMMARY
Embodiments described herein generally relate to articulating
expandable intervertebral implants for a human spine. Embodiments
described herein include an upper body, a lower body, an insert,
and a spacer. The upper body may include an upper portion and a
lower portion. A superior surface of the upper portion may engage a
first vertebra of the human spine. At least a portion of the
inferior surface of the upper portion of the upper body and at
least a portion of the superior surface of the lower portion may be
coupled to allow articulation of the upper body. The lower body may
include a superior surface and an inferior surface. The inferior
surface of the lower body may engage a second vertebra of the human
spine.
In some embodiments, the insert is configured to be positioned
between the superior surface of the lower body and the inferior
surface of the lower portion of the upper body before insertion of
the intervertebral implant between the first vertebra and the
second vertebra of the human spine. In certain embodiments, the
insert includes a recess. Translation or rotation of the insert may
increase a separation distance between the upper body and the lower
body of the intervertebral implant.
In some embodiments, the spacer is configured to be inserted
between the lower body and the lower portion of the upper body to
maintain at least a portion of the separation distance between the
upper body and the lower body or to maintain at least a portion of
the increased height of the intervertebral implant. In certain
embodiments, the spacer includes a protrusion. The protrusion may
be configured to substantially mate with the recess of the insert
to inhibit unintentional removal of the spacer from the
intervertebral implant during use. In some embodiments, a portion
of the spacer is configured to engage a portion of the
intervertebral implant such that full insertion of the spacer
between the lower body and the lower portion of the upper body
provides a tactile sensation to the surgeon inserting the spacer.
In some embodiments, a thickness of the spacer increases from one
side of the spacer to the other side of the spacer to achieve a
desired lordotic angle of the intervertebral implant. In certain
embodiments, the spacer includes an opening. The opening may be
threaded. A tool may be removably coupled to the opening to
facilitate insertion of the spacer between the lower body and the
lower portion of the upper body.
In some embodiments, the spacer includes an internal lip or an
external lip around at least a portion of the spacer. In certain
embodiments, the spacer includes a lip around at least a superior
portion or an inferior portion of the spacer. The lip may
facilitate insertion or retention of the spacer between the lower
body and the lower portion of the upper body. In some embodiments,
the lower portion of the upper body includes a lip to facilitate
insertion or retention of the spacer in the intervertebral implant.
In some embodiments, the lower body includes a lip configured to
facilitate insertion or retention of the spacer in the
intervertebral implant.
In some embodiments, the spacer may be configured to be press fit
or loose fit between the lower body and the lower portion of the
upper body. In certain embodiments, the spacer may be configured to
be reversibly or irreversibly locked in place between the lower
body and the lower portion of the upper body.
In further embodiments, features from specific embodiments may be
combined with features from other embodiments. For example,
features from one embodiment may be combined with features from any
of the other embodiments. In further embodiments, additional
features may be added to the specific embodiments described
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
Advantages of the present invention will become apparent to those
skilled in the art with the benefit of the following detailed
description and upon reference to the accompanying drawings in
which:
FIG. 1 depicts a top view of an embodiment of a cylindrical,
expandable implant.
FIG. 2A is a side cross-sectional view of the embodiment depicted
in FIG. 1.
FIG. 2B is a side cross-sectional view of the implant embodiment
depicted in FIG. 1.
FIG. 3A is a cross-sectional view of an embodiment of an expandable
implant in extension.
FIG. 3B is a cross-sectional view of an embodiment of an expandable
implant in flexion.
FIG. 4A is a cross-sectional view of an embodiment of an expandable
implant prior to expansion.
FIG. 4B is a cross-sectional view of an embodiment of an expandable
implant following expansion.
FIG. 4C is a cross-sectional view of an embodiment of an expandable
implant employing buttress screws to secure the device between
vertebrae.
FIG. 4D is a cross-sectional view of an embodiment of an expandable
implant employing an expansion plate with a securing keel to secure
the device between vertebrae.
FIG. 4E is a side perspective of an embodiment of an expandable
implant employing a securing keel.
FIG. 5 is a side perspective view illustrating placement of an
expandable implant in an intervertebral space.
FIG. 6A depicts a top view of an embodiment of a c-shaped,
expandable implant.
FIG. 6B is a top view of an embodiment of a c-shaped expandable
implant, illustrating insertion of expansion screws to expand the
implant.
FIG. 6C is a top view of an embodiment of a c-shaped, expandable
implant, illustrating insertion of a non-threaded expansion member
to expand the implant.
FIG. 6D is a top view of an embodiment of a c-shaped, expandable
implant with a posteriorly positioned expansion opening.
FIG. 7A is a cross-sectional view of an embodiment of an
expandable, articulating implant including an insert with
stops.
FIG. 7B is a cross-sectional view of the embodiment depicted in
FIG. 7A showing articulation of the implant.
FIG. 8A is a top view of an embodiment of a c-shaped, expandable
implant, illustrating the insertion of an expansion plate to expand
the implant.
FIG. 8B is a side cross-sectional view of an embodiment of a
c-shaped, expandable implant, illustrating the insertion of an
expansion plate to expand the implant.
FIG. 8C is a side cross-sectional view of an embodiment of an
expandable implant, featuring stabilizers.
FIG. 8D is a side cross-sectional view of an embodiment of an
expandable implant in flexion, featuring stabilizers.
FIG. 9A is a top view of an embodiment of an expandable cage.
FIG. 9B is a side cross-sectional view of an embodiment of an
expandable cage prior to expansion.
FIG. 9C is a side cross-sectional view of an embodiment of an
expandable following expansion.
FIG. 9D is a side cross-sectional view of an embodiment of an
expandable cage with a larger upper surface area prior to
expansion.
FIG. 9E is a side cross-sectional view of an embodiment of an
expandable cage with a larger upper surface area following
expansion.
FIG. 9F is a cross-sectional view of an embodiment of a cage that
is expandable in two directions.
FIG. 10A is a posterior view of an embodiment of a c-shaped
lordotic expandable implant.
FIG. 10B is a top view of an embodiment of a c-shaped lordotic
expandable implant.
FIG. 11A is a lateral view of an embodiment of a c-shaped lordotic
expandable implant prior to expansion.
FIG. 11B is a lateral view of an embodiment of a c-shaped lordotic
expandable implant following expansion.
FIG. 12A is a side cross-sectional view of an embodiment of an
expandable lordotic cage prior to expansion.
FIG. 12B is a side cross-sectional view of an embodiment of an
expandable lordotic cage following expansion.
FIG. 13A is a lateral view of an embodiment of a c-shaped lordotic
expandable implant with an inclined expansion member.
FIG. 13B is a side cross-sectional view of an embodiment of an
expandable lordotic cage with an inclined expansion member.
FIG. 14A is a perspective view of an embodiment of an expandable,
articulating implant with a spiral cam.
FIG. 14B is a cross-sectional view of the implant embodiment
depicted in FIG. 14A prior to expansion.
FIG. 14C is a cross-sectional view of the implant embodiment
depicted in FIG. 14A following expansion.
FIG. 15A is a top view of an embodiment of a c-shaped expandable,
articulating implant with a round insert.
FIG. 15B a side cross-sectional view of an embodiment of a c-shaped
implant with an expansion member/advancing element combination
prior to expansion.
FIG. 15C is a side cross-sectional view of an embodiment of a
c-shaped implant with an expansion member/advancing element
combination following expansion.
FIG. 16A is a perspective view of an embodiment of an expandable,
articulating implant before expansion.
FIG. 16B is a perspective view of an embodiment of an expandable,
articulating implant following expansion.
FIG. 17 is a perspective view of an embodiment of a portion of an
implant with a double-wedged expansion member.
FIG. 18A is a cross-sectional view of an embodiment of an
expandable, articulating implant with a wedged insert.
FIG. 18B is a top view of an embodiment of a spacer.
FIG. 19A is a perspective view of an embodiment of an expandable
cage with an elongated insert.
FIG. 19B is a cross-sectional view of the expandable cage
embodiment depicted in FIG. 19A.
FIG. 19C is a view of the inferior surface of the upper body of the
cage depicted in FIG. 19A.
FIG. 20A is a perspective view of an embodiment of a cage including
a cam and cam ramps.
FIG. 20B is a view of the inferior surface of the upper body of the
embodiment of the cage depicted in FIG. 20A.
FIG. 20C illustrates the use of an advancing element to advance the
cam onto the cam ramp of the cage embodiment depicted in FIG.
20B.
FIG. 20D is a cross-sectional view of an embodiment of an
articulating cage including a cam and cam ramps.
FIG. 21A depicts a perspective view of an embodiment of an
expandable, articulating cage with toothed engaging surfaces.
FIG. 21B depicts a perspective view of the cage depicted in FIG.
21A (without the toothed engaging surface) after expansion.
FIG. 22 depicts a perspective view of an embodiment of an insert
with four cam ramps.
FIG. 23 depicts a perspective view of an embodiment of a portion of
a cage with cam ramps and stabilizers.
FIG. 24A depicts a perspective view of an embodiment of a spacer
coupled to an insert of an implant.
FIG. 24B depicts a perspective view of an embodiment of a spacer
with a protrusion.
FIG. 24C depicts a perspective view of an embodiment of a spacer
with a protrusion and a lip.
FIG. 24D depicts a perspective view of an embodiment of an insert
with a recess for accepting a protrusion of a spacer.
FIG. 24E depicts a cross-sectional view of an embodiment of a
spacer with a lip coupled to an insert in an expandable cage.
FIG. 25 depicts a perspective view of an embodiment of insertion of
a spacer into an expanded cage.
FIG. 26A depicts a perspective view of an embodiment of insertion
of a spacer into an expanded cage.
FIG. 26B depicts a perspective view of an embodiment of the cage
depicted in FIG. 26A after insertion of the spacer.
FIG. 26C depicts a perspective view of an embodiment of the cage
depicted in FIG. 26A after insertion of the spacer.
FIG. 27 depicts a perspective view of an embodiment of an expanded
cage with a large profile spacer.
FIG. 28A is a side view of an embodiment of a facet replacement
device, featuring a rod with two washer-type heads.
FIG. 28B is a side view of an embodiment of a portion of a facet
replacement device, featuring a rod with a single washer-type
head.
FIG. 28C is a cross-sectional view of an embodiment of a pedicle
screw featuring a locking screw head.
FIG. 28D is a cross-sectional view of an embodiment of a pedicle
screw featuring a head-locking insert that allows translation and
rotation of a rod.
FIG. 29A is a side view of an embodiment of a portion of a facet
replacement device, featuring a rod having a ball joint.
FIG. 29B is a side view of an embodiment of a portion of a facet
replacement device featuring a retaining plate.
FIG. 29C is a top view of an embodiment of a portion of a facet
replacement device featuring a retaining plate.
FIG. 29D is a top view of an embodiment of a portion of a facet
replacement device featuring a combination multi-axial pedicle
screw and retaining bar with post-type pedicle screw system.
FIG. 29E is a side view of an embodiment of a post-type pedicle
screw.
FIG. 29F illustrates attachment of the retaining bar to the
post-type pedicle screw.
FIG. 30 is a posterior view of a portion of a human spine after
reconstruction and implantation of an embodiment of an artificial
functional spinal unit including an expandable implant and a facet
replacement device.
FIG. 31A is a perspective view of an embodiment of a portion of a
facet replacement device.
FIG. 31B is a cross-sectional view of the facet replacement device
depicted in FIG. 31A.
FIG. 31C is a cross-sectional view of the facet replacement device
depicted in FIG. 31A.
FIG. 31D is a perspective view of an embodiment of a reduced
diameter portion of a rod resting in a pedicle screw head of a
facet replacement device.
FIG. 32 is a perspective view of an embodiment of a portion of a
facet replacement device with a retainer to limit the motion of a
rod.
FIG. 33A is a perspective view of an embodiment of a portion of a
facet replacement device designed to couple to a plate with a
T-shaped cross section.
FIG. 33B is a cross-sectional view of the facet replacement device
depicted in FIG. 33A.
FIG. 34A is a perspective view of an embodiment of a portion of a
facet replacement device including a pedicle screw with a ball
joint.
FIG. 34B is a cross-sectional view of the facet replacement device
depicted in FIG. 34A.
FIG. 34C is a cross-sectional view of the facet replacement device
depicted in FIG. 34A.
FIG. 35 is a perspective view of an instrument for installing and
expanding an implant.
FIG. 36 is a detail view of a distal end of an instrument for
installing and expanding an implant.
FIG. 37 is a detail view of a proximal end of an instrument for
installing and expanding an implant.
FIG. 38 is a perspective view of an expandable implant held by an
instrument including a holding device and expansion driver.
FIG. 39 is a perspective view of an instrument for installing an
expandable implant including a spacer.
FIG. 40 is a perspective top view of an expandable implant held by
an instrument with a partially inserted spacer.
FIG. 41 is a perspective bottom view of an expandable implant with
a partially inserted spacer.
FIG. 42 is a perspective view of a holding device including
opposing arms with ball detent mechanisms.
FIG. 43 is a perspective view of a holding device including
opposing arms coupled by a coil spring.
FIG. 44 is a perspective view of a holding device including
opposing spring arms.
FIG. 45 is a perspective view of a holding device with shape memory
alloy arms.
FIG. 46 is a perspective view of an implant held in a holding
device including upper and lower holding arms.
FIGS. 47A-47D illustrate use of an instrument to expand an implant
and install a spacer.
FIG. 48 is a perspective view of a distal end of an instrument
including a holding device with a slide.
FIG. 49 is a perspective view of an instrument with a holding
device coupled to a control member.
FIG. 50A is a side view of a dual rod instrument during guided
advancement of a spacer.
FIG. 50B is a side view of a dual rod instrument with one rod
positioned to impact the spacer between upper and lower bodies of
an implant.
FIG. 51 is a cross-sectional view of an instrument including a
driving portion that directly engages an insert for expanding an
implant.
FIGS. 52A and 52B are side views of an instrument including
multiple rods with threaded ends.
FIG. 53 is a schematic end view of a head of a fastener for a
spinal system.
FIG. 54 is a schematic end view of a driver for a fastener of a
spinal system.
While the invention may be susceptible to various modifications and
alternative forms, specific embodiments thereof are shown by way of
example in the drawings and will herein be described in detail. The
drawings may not be to scale. It should be understood, however,
that the drawings and detailed description thereto are not intended
to limit the invention to the particular form disclosed, but to the
contrary, the intention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the present
invention as defined by the appended claims.
DETAILED DESCRIPTION
As used herein, "implant" generally refers to an artificial
intervertebral implant or cage. The shape and/or size of an implant
or other device disclosed herein may be chosen according to factors
including, but not limited to, the surgical approach employed for
insertion (e.g., anterior or posterior), the intended position in
the spine (e.g., cervical or lumbar), and a size of the patient.
For example, cervical implants may range from about 6 mm to about
11 mm in height, and lumbar implants may range from about 10 mm to
about 18 mm in height. Heights outside these ranges may be used as
required by a patient's anatomy. In general, implants with a
substantially round cross section may range from about 14 mm to
about 26 mm in diameter, and implants with a substantially square
cross section may range from a size of about 14 mm square to a size
of about 26 mm square. Implants that are substantially rectangular
or trapezoidal may range from about 8 mm to about 12 mm along short
side of the implant to about 24 mm to about 30 mm along a long side
of the implant. As used herein, "c-shaped" implants generally refer
to implants with an arcuate shape. Some c-shaped implants may be
slightly curved (e.g., "banana-shaped"), while other c-shaped
implants may have a higher degree of curvature (e.g., more closely
approximating a "c").
It is to be understood that implants described herein may include
features not necessarily depicted in each figure. In some
embodiments, an endplate engaging surface of any implant may have
regularly or irregularly spaced protrusions of uniform or various
shapes and sizes to facilitate retention of the implant in a
desired position between vertebrae. For example, an endplate
engaging surface of an implant may include teeth or ridges. In some
embodiments, members of an implant may include one or more openings
to accommodate packing of bone graft material and/or to allow for
bone ingrowth. In certain embodiments, one or more surfaces of an
implant may include material, such as osteoconductive scaffolding,
to enhance integration of the implant in a patient's spine. In some
embodiments, a substance to be delivered to a patient's body may be
included in a portion of the implant for delivery to the insertion
site. In certain embodiments, implants depicted herein may include
features allowing the implant to provide a desired lordotic angle
(e.g., up to about 15.degree.) between vertebrae.
As used herein, an "expandable" implant generally refers to an
implant designed such that a height of the implant and/or a
separation distance between two parts of the implant may be
increased. In some embodiments, an implant may be expanded after
insertion of the implant in a human spine. In certain embodiments,
a height of an implant may be decreased after the implant has been
expanded during insertion in a human spine. In other embodiments,
expansion of an implant may be substantially irreversible after
insertion in a human spine.
As used herein, an "articulating" implant generally refers to an
implant designed such that at least two members of the implant are
capable of undergoing rotational motion with respect to each other
in at least one direction after insertion in a human spine. In some
embodiments, one or more members of an articulating implant may be
capable of rotating in more than one direction with respect one or
more other members of the implant after insertion in a human spine
to allow, for example, anterior-posterior rotation and/or lateral
bending. In some embodiments, rotation may occur about fixed axes.
In certain embodiments, an axis of rotation may change as one
member of an implant rotates relative to another member of the
implant. In some embodiments, one or more members of an
articulating implant may be capable of translating with respect to
one or more other members of the implant. As used herein, an
articulating implant may also be described as "functional" or
"dynamic".
Implant embodiments depicted herein may be expandable and/or
articulating. In certain embodiments, expansion of an implant after
insertion in a human spine may allow articulation of the implant.
That is, the implant may not display articulating motion before
expansion of the implant in a human spine. In other embodiments,
expansion of an implant after insertion in a human spine may allow
an increased range of motion (increased articulation) between at
least two members of the implant. As used herein, "insertion" of an
implant in a human spine may refer to assembly, insertion,
positioning, and/or expansion of the implant.
As used herein "facet replacement device" generally refers to a
facet replacement device. For simplicity, a portion of a facet
replacement device may generally be referred to as a facet
replacement device. The facet replacement devices disclosed herein
generally allow for rotational and/or translational motion of one
or more portions of the facet replacement device including, but not
limited to, a plate or elongated member (e.g., rod, bar, rail).
Pedicle screws of facet replacement devices disclosed herein may
retain multi-axial character after insertion of the facet
replacement device. As used herein, "pedicle screw" refers to a
portion of a facet replacement device that couples to bone. As used
herein, "pedicle screw head" refers to a portion of a facet
replacement device that accepts an elongated member. As used
herein, "pedicle screw" and "pedicle screw head" may be separate
components that may be assembled for use in a facet replacement
device.
As used herein, "coupled" includes a direct or indirect coupling
unless expressly stated otherwise. For example, a control member
may be directly coupled to a driver or indirectly coupled by way of
an intermediate shaft. As used herein, "member" includes an
individual member or a combination of two or more individual
members. A "member" may be straight, curved, flexible, rigid, or a
combination thereof. A member may have any of various regular and
irregular forms including, but not limited to, a rod, a plate, a
disk, a cylinder, a disk, or a bar.
An implant may be constructed of one or more biocompatible metals
having a non-porous quality (e.g., titanium) and a smooth finish.
In some embodiments, an implant may be constructed of ceramic
and/or one or more other suitable biocompatible materials, such as
biocompatible polymers. Biocompatible polymers include, but are not
limited to, polyetheretherketone resin ("PEEK"). In certain
embodiments, an implant may be constructed of a combination of one
or more biocompatible metals and one or more ceramic and/or
polymeric materials. For example, an implant may be constructed of
a combination of biocompatible materials including titanium and
PEEK.
FIG. 1 depicts a top view of an embodiment of an expandable,
articulating implant. Implant 100 may be substantially cylindrical.
FIGS. 2A and 2B depict a side cross-sectional view of implant 100.
In some embodiments, implant 100 may include upper body 102 and
lower body 104. As used herein, "body" may be of unitary
construction or may include two or more members. References to
"upper body" and "lower body" are chosen for convenience of
description of the figures. In some embodiments, an implant may be
inserted in a human spine with the "upper body" superior to the
"lower body". In some embodiments, an implant may be inserted in a
human spine with the "lower body" superior to the "upper body". In
certain embodiments, upper and lower bodies of an implant may be
substantially interchangeable. Similarly, "inferior" and "superior"
surfaces are also named for convenience of description and may
assume "superior" and "inferior" positions, respectively, upon
insertion.
Implant 100 may include upper body 102 and lower body 104 in a
substantially planar configuration. In some embodiments, superior
surface 106 of upper body 102 and inferior surface 108 of lower
body 104 may include (e.g., be coupled to) osteoconductive
scaffolding 110 (e.g., an osteoconductive mesh structure).
Vertebral bone from a patient's spine may grow through
osteoconductive scaffolding 110 after insertion of implant 100. In
some embodiments, osteoconductive scaffolding 110 may include
spines and/or barbs that project into and secure against the bony
endplates of the adjacent vertebral bodies upon expansion of the
implant, reducing the possibility of subluxation and/or
dislocation.
In some embodiments, a shape of recess 116 and insert 118 may be
substantially the same as a shape of upper body 102 and/or lower
body 104. In certain embodiments, a shape of insert 118 may be
different from a shape of upper body 102 and/or lower body 104. For
example, a shape of insert 118 may be oval or round, and upper body
102 and/or lower body 104 may be c-shaped. Implant 100 may include
expansion member 124. Expansion member 124 may be inserted into
opening 126 to elevate insert 118 from recess 116.
In some embodiments, at least a portion of inferior surface 112 of
upper body 102 may be concave. In certain embodiments, superior
surface 114 of lower body 104 may include recess 116. Recess 116
may include, but is not limited to, a channel or groove. In some
embodiments, recess 116 may have a rectangular cross section that
extends along lower body 104 in the medial-lateral direction. In
certain embodiments, a shape of recess 116 may be substantially the
same as a shape of upper body 102 and/or lower body 104. Insert 118
may be positioned in recess 116 on superior surface 114 of lower
body 104. In some embodiments, inferior surface 120 of insert 118
may be substantially flat. In some embodiments, at least a portion
of superior surface 122 of insert 118 may be convex. A convex
portion of superior surface 122 of insert 118 may articulate with a
concave portion of inferior surface 112 of upper body 102, allowing
rotation of upper body 102 with respect to lower body 104.
In some embodiments, one or more expansion members may be used to
increase a height of an implant and/or increase a separation
distance between two or more members of an implant by engaging a
portion (e.g., an insert) of the implant. In some embodiments, an
expansion member may be a part of the implant. That is, the
expansion member may remain coupled to the implant after insertion
of the implant in a human spine. For example, expansion members may
include, but are not limited to, screws, plates, wedges, and/or a
combination of two or more of these elements. In some embodiments,
an expansion member may be a tool, instrument, or driver that is
used to expand the implant during insertion but does not remain as
part of the implant following insertion. In certain embodiments, an
expansion member may be used to elevate an insert with respect to
the lower body of the implant, thereby increasing a height of the
implant and/or increasing a separation distance between two or more
members of the implant. In certain embodiments, an expansion member
may be used to translate and/or rotate an insert with respect to a
body of the implant (e.g., upper body, lower body), thereby
increasing a height of the implant and/or increasing a separation
distance between two or more members of the implant.
As depicted in FIGS. 2A and 2B, expansion member 124 may be a
screw. Expansion member 124 may be inserted through opening 126 and
below insert 118 to elevate the insert from lower body 104. In some
embodiments, opening 126 may be threaded to accept a threaded
expansion member. In certain embodiments, opening 126 may include
features (e.g., notches) to allow stepwise insertion of an
expansion member. For example, an expansion member may enter
opening 126 in a ratcheting motion. In some embodiments, a void
space may be created between insert 118 and the bottom of recess
116 adjacent to the expansion member.
FIGS. 3A and 3B depict side cross-sectional views of implant 100
after insertion of expansion member 124 (e.g., after expansion of
the implant) such that concave inferior surface 112 of upper body
102 is able to articulate with convex superior surface 122 of
insert 118. FIG. 3A depicts implant 100 with upper body 102 rotated
with respect to lower body 104 to undergo extension. FIG. 3B
depicts implant 100 with upper body 102 rotated with respect to
lower body 104 to undergo flexion. In some embodiments, stabilizers
128 may be used to maintain alignment of upper body 102 and lower
body 104 during insertion, expansion, and/or articulation of
implant 100. Stabilizers 128 may include, but are not limited to,
cables, retaining pegs, elastomeric bands, springs, and/or
combinations thereof.
FIGS. 4A and 4B illustrate the expansion of implant 100 in more
detail. As shown in FIG. 4A, prior to expansion of implant 100,
upper body 102 may rest upon lower body 104. Inferior surface 120
of insert 118 may rest upon the bottom of recess 116, which extends
along a portion of lower body 104. In some embodiments, a surface
of insert 118 may have angled portion 130. In some embodiments, an
angled portion may be a wedge-shaped portion. In certain
embodiments, an angled portion may include a curved surface or
other surface to facilitate elevation of insert 118 from lower body
104. Angled portion 130 may facilitate the lifting of insert 118,
allowing expansion member 124 to engage inferior surface 120 of
insert 118. Following insertion of expansion member 124 (e.g.,
following expansion to a desired intervertebral disc height 132),
inferior surface 120 of insert 118 may rest upon the expansion
member with upper body 102 raised above lower body 104, as depicted
in FIG. 4B.
After expansion of implant 100, the implant may be secured in place
in a human spine with one or more fasteners (e.g., one or more
buttress screws). FIG. 4C illustrates an embodiment utilizing
fastener 134. Lower body 104 may include portion 136 with one or
more openings 138 defined therethrough. One or more fasteners 134
may be inserted through portion 136 and secured into a vertebral
body. In some embodiments, fastener 134 may be a screw (e.g., a
buttress screw).
In some embodiments, an implant may be secured in place with a
portion of an expansion member. As shown in FIG. 4D, expansion
member 140 may include portion 142 with one or more openings 138
defined therethrough. In some embodiments, portion 142 may be a
keel. After expansion member 140 is impacted into place, one or
more screws 134 may be inserted through portion 142 and secured
into a vertebral body. Expansion member 140 and lower body 104 may
also include complementary engaging portion 144 to secure expansion
member 140 with lower body 104.
FIG. 4E illustrates implant 100 secured between vertebrae of a
human spine. One end of portion 142 may be secured onto lower body
104 of implant 100. Portion 142 may be rotated after placement of
the device in the intervertebral space. After rotation of portion
142, the portion is secured to the vertebral body above or below
implant 100 with one or more fasteners 134 (e.g., screws). FIG. 5
depicts implant 100 following insertion in a spinal column. In some
embodiments, implant 100 may be posteriorly inserted and expanded
through void space 146 created by removal of a facet joint.
FIG. 6A depicts a top view of an embodiment of a c-shaped
expandable implant. Implant 148 may include insert 118. In some
embodiments, insert 118 may be substantially the same as a shape of
an upper body and/or lower body of implant 148. In certain
embodiments, a shape of insert 118 may be different from a shape of
upper body 102 and/or lower body 104. For example, a shape of
insert 118 may be oval or round, and upper body 102 and/or lower
body 104 may be c-shaped. Implant 148 may include two or more
expansion members 124. Expansion members 124 may be inserted into
openings 126 to elevate insert 118 from recess 116.
FIGS. 6B and 6C illustrate the insertion of expansion members into
c-shaped implants. In the embodiment depicted in FIG. 6B, expansion
members 124 for implant 148 may be screws. One or more expansion
members 124 may be inserted through one or more openings 126. In
some embodiments, one or more openings 126 may be threaded. In
certain embodiments, as shown in FIG. 6C, implant 150 may include
expansion member 152. Expansion member 152 may be an elongated or
curved member sized and/or shaped for insertion through opening
126. In some embodiments, expansion member 152 may have an angled
or wedge portion. Opening 126 may be non-threaded. Expansion member
152 may be impacted or driven through opening 126 into recess 116
to engage insert 118. Recess 116 may be an arcuate channel or a
groove shaped and/or sized to facilitate insertion of expansion
member 152 before or after implant 150 has been positioned between
vertebrae of a human spine. A shape of expansion member 152 may be
complementary to a shape of recess 116. Engaging insert 118 with
expansion member 152 may elevate the insert from the lower body of
implant 150, increasing a separation distance between the upper
body and the lower body of the implant. In some embodiments, member
154 may be used to retain expansion member 152 in recess 116.
Member 154 may be, for example, a cap or set screw that fits
through opening 126 into a portion (e.g., a threaded portion) of
recess 116.
FIG. 6D depicts an alternative embodiment for posteriorly securing
an expansion member in a c-shaped implant. Expansion member 156 may
be an expansion plate. Expansion member 156 may be inserted through
opening 126 of implant 158. Expansion member 156 may be inserted
posteriorly through opening 126 to slidingly engage insert 118 in
implant 158 in the medial-lateral direction. After expansion,
member 160 may be inserted in recess 116. In some embodiments,
member 160 may be a retainer plate. In some embodiments, member 160
may substantially fill recess 116. In certain embodiments, member
160 may include a securing device such as, for example, a
screw.
FIGS. 7A and 7B depict a cross-sectional view of another embodiment
of an expandable, articulating implant. Implant 162 may include
upper body 102, lower body 104, insert 164, expansion member 152,
and set screw 166 or similar device. Insert 164 may include one or
more stops 168. In some embodiments, stop 168 may be a lip or ledge
around a circumference of insert 164. In certain embodiments,
insert 164 may include angled portion 130. In certain embodiments,
expansion member 152 may include angled portion 170. Before
insertion of expansion member 152 into recess 116, inferior surface
112 of upper body 102 may rest on superior surface 114 of lower
body 104.
With insert 164 positioned in recess 116 of lower body 104,
expansion member 152 may be inserted into recess 116. Angled
portion 170 of expansion member 152 may engage angled portion 130
of insert 164 and expand implant 162. In some embodiments, set
screw 166 may be used to inhibit backout of expansion member 152
after insertion of the expansion member. In certain embodiments,
set screw 166 may be used to advance expansion member 152 as well
as to inhibit backout of the expansion member.
After expansion of implant 162, a separation distance between
inferior surface 112 of upper body 102 and superior surface 114 of
lower body 104 may allow articulation of the upper body with convex
superior surface 122 of insert 164. FIG. 7A depicts implant 162
after expansion. As depicted in FIG. 7A, upper body 102 is
substantially parallel to lower body 104. FIG. 7B depicts implant
162 following articulation of upper body 102 with respect to lower
body 104. As depicted in FIG. 7B, stops 168 may limit an angular
range of motion of upper body 102 with respect to lower body 104.
In some embodiments, a shape and/or thickness of stops 168 may
limit a range of rotation of upper body 102 with respect to lower
body 104 to less than about 20.degree.. For example, a range of
rotation of upper body 102 may be limited to less than about
5.degree., less than about 10.degree., or less than about
15.degree.. A range of rotation may depend upon, for example, a
shape (e.g., round, ellipsoidal, etc.) of the convex portion of
superior surface 122 of insert 164.
FIGS. 8A and 8B depict different cross-sectional views of an
embodiment of an expandable, articulating c-shaped implant. As
shown in FIG. 8A, implant 172 depicts recess 116 designed to accept
arcuate expansion member 152. Implant 172 may have opening 126 on
an end (e.g., a short side) of the implant. Expansion member 152
may be impacted into place through opening 126 to elevate insert
118 from lower body 104 after implant 172 has been positioned in an
intervertebral space. Recess 116, as well as expansion member 152,
may have substantially the same shape (e.g., substantially the same
curvature) as a portion of the upper body and/or the lower body of
implant 172. In some embodiments, a portion of insert 118 may be
oval or round (e.g., ellipsoidal, spherical) to allow improved
biomechanical motion of the implant. In some embodiments, a bottom
of recess 116 may include a feature (e.g., an integral part of the
lower body or an element coupled to a portion of the lower body)
designed to retain expansion member 152 in position after
expansion. For example, as depicted in FIG. 8B, surface 174 of
recess 116 may include lip 176 or other feature designed to retain
expansion member 152 in the recess. During insertion of implant
172, a surgeon may force expansion member 152 over lip 176 into
place. Passage of expansion member 152 over lip 176 and into place
may allow the surgeon to feel when expansion member 152 has been
properly inserted. In some embodiments, lip 176 may inhibit
dislocation of the implant (e.g., backout of expansion member
152).
FIGS. 8C and 8D depict cross-sectional views of an embodiment of an
expandable, articulating implant. Implant 178 may include
stabilizers 180. Stabilizers 180 may be coupled to lower body 104
and may extend from the lower body into openings 182 in upper body
102. Stabilizers 180 and/or openings 182 may be of various sizes
and/or shapes. For example, Stabilizers 180 may be substantially
round and openings 182 may be substantially oval, allowing
torsional mobility of upper body 102. In some embodiments,
stabilizers 180 may be captive. Stabilizers 180 may inhibit
dislocation of upper body 102 from lower body 104 during flexion,
extension, and/or torsional motion of implant 178. As shown in FIG.
8D, when implant 178 is flexed or extended, stabilizers 180 may
inhibit dislocation of upper body 102 from lower body 104.
The disclosed techniques of expanding an implant by insertion of an
expansion member may also be employed to expand a PLIF or TLIF
cage. FIGS. 9A-9C depict views of an embodiment of an expandable
cage. FIG. 9A depicts a top view of cage 184. FIG. 9B depicts a
cross-sectional view of cage 184 before expansion. In some
embodiments, cage 184 may include cage element 186 and insert 188.
Insert 188 may be positioned in cage element 186. In certain
embodiments, cage element 186 may include osteoconductive
scaffolding 110. For example, cage element 186 may include
osteoconductive scaffolding 110 on inferior surface 190. An
osteoconductive substance may be placed in osteoconductive
scaffolding 110 to promote bone growth into cage 184. In some
embodiments, cage element 186 may include opening 192 through
superior surface 194.
In some embodiments, insert 188 may include member 196 having
inferior surface 198 and superior surface 200. In some embodiments,
member 196 may be substantially planar (e.g., a plate). In certain
embodiments, osteoconductive scaffolding 202 may be coupled to
superior surface 200 of member 196. Member 196 may include angled
portion 130. Angled portion 130 may facilitate expansion of cage
184 (e.g., elevation of insert 188) upon insertion of expansion
member 204. Expansion member 204 may be inserted into opening 206
of cage element 186 and advanced (e.g., impacted, driven) to engage
angled portion 130 of member 196. FIG. 9C depicts a cross-sectional
view of expanded cage 184. In some embodiments, lip 176 may inhibit
dislocation of expansion member 204 after expansion of cage 184. In
certain embodiments, lip 176 and/or one or more other features may
secure expansion member 204 in cage element 186 in such a way that
a surgeon may sense tactilely when the expansion member is fully
inserted in cage 184.
FIGS. 9D and 9E depict cross-sectional views of an embodiment of an
expandable cage. FIG. 9D depicts cage 208 before expansion. Insert
210 of cage 208 may include osteoconductive scaffolding 212 coupled
to superior surface 214 of member 216. In some embodiments,
osteoconductive scaffolding 212 may have a T-shaped cross-section,
such that the osteoconductive scaffolding rests upon superior
surface 218 of cage element 220, providing an increased surface
area between the osteoconductive scaffolding and the bony endplates
within the intervertebral space.
In some embodiments, expandable cages may be expanded in two or
more dimensions. FIG. 9F depicts an embodiment of a cage that may
be expanded in two dimensions. Cage 222 may include cage element
186 and inserts 188. Cage element 186 may include opening 224
through inferior surface 190 as well as opening 192 through
superior surface 194. Two inserts 188 may be positioned in cage
element 186. As expansion member 204 is inserted into cage element
186 between inserts 188, the inserts may be forced through openings
192, 224 to engage the bony endplates within the intervertebral
space.
FIGS. 10A, 10B, 11A, and 11B depict an embodiment of a lordotic,
c-shaped expandable, articulating implant. The lumbar spine is
lordotic, thus the anterior disc height is naturally larger than
the posterior disc height. Therefore, an expandable implant for the
lumbar spine may advantageously expand into a lordotic position.
FIG. 10A depicts a posterior view of implant 226. FIG. 10B depicts
a top view of implant 226. FIGS. 11A and 11B depict cross-sectional
views of implant 226 before and after expansion of the implant,
respectively.
Implant 226 may include upper body 228 and lower body 230. Lower
body 230 may include two or more members. In some embodiments,
members of lower body 230 may be coupled (e.g., hinged). Portions
of upper body 228 and lower body 230 may be substantially parallel
before expansion of implant 226. In some embodiments, superior
surface 106 of upper body 228 and inferior surface 108 of lower
body 230 may include osteoconductive scaffolding 110. In certain
embodiments, at least a portion of inferior surface 112 of upper
body 228 may be substantially concave.
Lower body 230 may include lower portion 232 and upper portion 234.
In some embodiments, lower portion 232 and upper portion 234 of
lower body 230 may be coupled with hinge 236. Hinge 236 may
effectively fix posterior disc height 238 (shown in FIG. 11B). In
certain embodiments, inferior surface 240 of upper portion 234 may
be substantially flat. In certain embodiments, at least a portion
of superior surface 242 of upper portion 234 may be convex. Lower
portion 232 and inferior surface 240 of upper portion 234 may be
substantially parallel prior to expansion. In some embodiments,
lifting mechanism 244 may be located proximate anterior end 246 of
lower portion 232. Following insertion of implant 226 in an
intervertebral space, lifting mechanism 244 may be engaged to
increase a height of anterior end 246 of implant 226. Increasing a
height of anterior end 246 of implant 226 may provide a desired
anterior disc height 248 and proper lordosis. As depicted in FIGS.
11A and 11B, anterior end 246 of upper portion 234 may include
notch 250. Notch 250 may engage lifting mechanism 244 to secure a
height of anterior end 246 of implant 226 following expansion.
In some embodiments, at least a portion of inferior surface 112 of
upper body 228 may be concave. A concave portion of inferior
surface 112 of upper body 228 may articulate with a convex portion
of superior surface 242 of upper portion 234. When viewed in the
medial or lateral direction, as shown in FIGS. 11A and 11B, upper
body 228 may include extension 252 for coupling to elongated member
254. In some embodiments, elongated member 254 may couple upper
body 228 to upper portion 234 of lower body 230, thus reducing a
possibility of dislocation. FIG. 11B depicts the posterior
placement of hinge 236 and anterior placement of lifting mechanism
244, with elongated member 254 positioned through upper body 228
and upper portion 234 of lower body 230.
A lifting mechanism may also be used to achieve desired lordosis
with expandable PLIF and TLIF cages, as shown in FIGS. 12A and 12B.
FIGS. 12A and 12B depict side cross-sectional views of cage 256
before and after expansion, respectively. Cage 256 may include
upper body 258 and lower body 260. In some embodiments, hinge 262
may posteriorly couple upper body 258 to lower body 260. In certain
embodiments, hinge 262 may fix posterior disc height 238 after
expansion of cage 256. Superior surface 264 of upper body 258 and
inferior surface 266 of lower body 260 may include osteoconductive
scaffolding 110. Lifting mechanism 244 may be engaged to expand
cage 256. In some embodiments, lifting mechanism 244 may engage
notch 250 after expansion, reducing the possibility for dislocation
after insertion and expansion of cage 256. A height of lifting
mechanism 244 may be chosen to achieve a desired anterior disc
height 248 (e.g., to achieve proper lordosis).
FIG. 13A depicts a cross-sectional view of an expandable,
articulating lordotic implant. FIG. 13B depicts a cross-sectional
view of an embodiment of an expandable lordotic cage. Implant 268
in FIG. 13A and cage 270 in FIG. 13B both include expansion member
272 to achieve proper lordosis. In some embodiments, expansion
member 272 is generally wedge-shaped. In certain embodiments,
posterior end 274 of expansion member 272 may include angled
portion 276. Angled portion 276 may facilitate expansion of implant
268 and cage 270. Protrusion 280 may be located on superior surface
278 of the anterior end of expansion member 272. As show in FIG.
13A, expansion member 272 may be inserted between upper portion 234
and lower portion 232 of lower body 230. Protrusion 280 may engage
notch 250 to secure a height of implant 268 and cage 270 following
expansion. Lip 176 or other feature may be located on an anterior
end of superior surface 282 of lower portion 232 to reduce the
potential of dislocation of expansion member 272.
FIG. 14A depicts a perspective view of an embodiment of an
expandable, articulating implant. Implant 284 may be of any size
and/or shape known in the art. FIGS. 14B and 14C depict
cross-sectional views of implant 284 before and after expansion,
respectively. Implant 284 may include upper body 286, lower body
288, and elongated member 290. In some embodiments, lower body 288
may include channel 294. Lower body 288 may include openings 296 on
opposing walls for receiving elongated member 290. In certain
embodiments, elongated member 290 may traverse a portion (e.g., a
length) of implant 284.
In some embodiments, elongated member 290 may include cam portion
298. In certain embodiments, cam portion 298 may include a spiral
cam portion. Cam portion 298 may include an arcuate surface that
resides within channel 294 of lower body 288. In some embodiments,
cam portion 298 may be coupled to elongated member 290. In certain
embodiments, cam portion 298 may form an integral part of elongated
member 290. In some embodiments, cam portion 298 may wrap partially
around elongated member 290 with increasing thickness. In some
embodiments, as depicted in FIG. 14B, implant 284 may be in an
unexpanded position when cam portion 298 rests at the bottom of
channel 294. When elongated member 290 is rotated, cam portion 298
may spin upward to expand implant 284. FIG. 14C depicts a
cross-sectional view of expanded implant 284.
Superior surface 300 of upper body 286 may contact the bony surface
of a human vertebra after insertion of implant 284 in a human
spine. In some embodiments, an inferior surface of upper body 286
may articulate with the arcuate surface of cam portion 298. In
certain embodiments, upper body 286 may move back and forth against
the arcuate surface of cam portion 298. This movement may allow
biomechanical motion in a human spine in which implant 284 has been
inserted and expanded. In some embodiments, elongated member 290
may be held in place in openings 296 to fix a height of implant 284
after expansion. For example, a ratcheting device or fastener
(e.g., a set screw) may be used to fix a position of elongated
member 290. In certain embodiments, superior surface 300 of upper
body 286 and/or inferior surface 302 of lower body 288 may be
coupled to osteoconductive scaffolding.
FIGS. 15A-15C depict an embodiment of a c-shaped expandable,
articulating implant. FIG. 15A depicts a top view of implant 304
with insert 306. In some embodiments, a portion of insert 306 may
be substantially round, providing a close approximation to natural
biomechanical motion. FIGS. 15B and 15C illustrate side
cross-sectional views of implant 304 before and after expansion,
respectively. Expansion member 308 may be inserted through opening
310. In some embodiments, opening 310 may be threaded. Advancing
element 312 may be inserted in opening 310 following insertion of
expansion member 308. Advancing element 312 may be used to advance
expansion member 308 into position below insert 306. In some
embodiments, advancing element 312 may remain in recess 314 to
inhibit dislocation of expansion member 308 after expansion of
implant 304. Use of advancing element 312 (e.g., a set screw) to
advance expansion member 308 into place may reduce impaction during
positioning of the expansion member. Reducing impaction during
positioning of expansion member 308 may reduce stress on portions
of a patient's body during the insertion procedure. It should be
noted that the expansion member/advancing element combination may
be employed with any of the disclosed implants, including
cages.
FIGS. 16A and 16B depict perspective views of an embodiment of a
c-shaped expandable, articulating implant before and after
expansion, respectively. As shown in FIG. 16A, implant 316 may
include insert 306 and expansion member 308. Insertion of expansion
member 308 is achieved by movement of advancing element 312 through
opening 310 in an end of implant 316. Advancing expansion member
308 with advancing element 312 or other device (e.g., a threaded
driver) rather than impacting the expansion member may allow a
smaller expansion member to be used. Using a smaller expansion
member may require a shorter access to the implant, allowing an
implant to be positioned in a final TLIF position and then
expanded. For example, a smaller expansion member may require a
shorter access to the implant. Raising insert 306 with expansion
member 308 may increase a height of implant 316. Increasing a
height of implant 316 may increase a range of articulation of the
implant after insertion of the implant in a human spine.
FIG. 17 depicts a perspective view of an embodiment of a portion of
an expandable implant. Implant 318 may include expansion member
320. Expansion member 320 may be advanced with advancing element
322. As depicted in FIG. 17, advancing element 322 may be a screw.
In some embodiments, advancing element 322 may engage expansion
member 320 from a side (e.g., anterior side, posterior side) of
implant 318. In some embodiments, expansion member 320 may include
two angled portions. Angled portion 324 may engage a portion of
implant 318 (e.g., an insert or a portion of an upper body or a
lower body). Advancing element 322 may engage angled portion 326,
thus allowing a component of the force from the advancing element
to increase a height of implant 318. Accessing expansion member 320
from a longer side (e.g., posterior side) of implant 318 (PLIF
approach) may advantageously require a smaller incision and/or
cause less tissue damage during insertion of the implant than
accessing the expansion member from shorter end of the implant
(TLIF approach).
FIG. 18A depicts an embodiment of a c-shaped expandable,
articulating implant designed to accept a spacer between an upper
body and a lower body of the implant after expansion. Upper body
328 of implant 330 may include upper portion 332 and lower portion
334. Upper portion 332 and lower portion 334 may both have
substantially the same c-shape. In some embodiments, superior
surface 336 of upper portion 332 may contact a bony surface of a
vertebral body after insertion of implant 330 in a human spine. At
least a portion of inferior surface 338 of upper portion 332 may be
concave. At least a portion of superior surface 340 of lower
portion 334 may be convex. In some embodiments, inferior surface
338 of upper portion 332 may articulate with superior surface 340
of lower portion 334.
In some embodiments, inferior surface 342 of lower portion 334 may
include angled portion 344. As depicted in FIG. 18A, angled portion
344 may be a downward projecting ramp. In certain embodiments,
angled portion 346 of expansion member 348 may engage angled
portion 344 of lower portion 334 during insertion of the expansion
member. After expansion of implant 330, spacer 350 may be inserted
in gap 352 between lower portion 334 of upper body 328 and lower
body 354. In some embodiments, spacer 350 may be a shim. In certain
embodiments, a superior surface of lower body 354 may include one
or more guides 356. Guides 356 may include, but are not limited to,
protrusions, keyways, rails, grooves, ridges, notches, and/or
combinations thereof. Guides 356 may align spacer 350 during
insertion of the spacer. In some embodiments, guides 356 may
inhibit dislocation of spacer 350 after insertion of the
spacer.
FIG. 18B depicts a top view of an embodiment of spacer 350. In some
embodiments, spacer 350 may have substantially the same shape
and/or profile as upper body 328 and/or lower body 354 of implant
330. In certain embodiments, spacer 350 may be sized such that the
spacer is substantially flush with an outside edge of implant 330.
In other embodiments, spacer 350 may protrude from implant 330
(e.g., from a side surface of implant 330) to facilitate alignment
and placement of the spacer in the implant. In some embodiments,
spacer 350 may include one or more guides 358. Guides 358 may
include, but are not limited to, grooves, keyways, rails, ridges,
protrusions, notches, and/or combinations thereof. Guides 358 on
spacer 350 may be complementary to guides on a portion (e.g., upper
body, lower body) of an implant.
A height of a spacer may be chosen to provide a desired expanded
height of an implant. A height of a spacer may be, for example, 2
mm, 3 mm, 4 mm, or greater. Spacer height may be chosen to achieve
a desired height of an implant in a patient's spine. In some
embodiments, a spacer with a variable thickness may be used to
provide lordosis to an implant. In some embodiments, a spacer may
be constructed of biocompatible metal (e.g., titanium). In certain
embodiments, a spacer may be constructed of the same material as an
implant into which the spacer is to be inserted. In other
embodiments, a spacer may include elastomeric material (e.g.,
silicone) to absorb shock and/or allow additional bending.
FIG. 19A depicts a perspective view of an embodiment of an
expandable implant with an elongated, rotating insert following
expansion. Implant 360 may include upper body 362, lower body 364,
insert 366, and advancing element 368. Intended placement of
implant 360 in the spine may determine a shape of upper body 362
and lower body 364 (e.g., c-shaped, round). Superior surface 370 of
lower body 364 may include recess 372. In some embodiments, recess
372 may be a channel. Insert 366 may be positioned in recess 372.
Insert 366 may remain in recess 372 during insertion and expansion
of implant 360. In some embodiments, inferior surface 374 of insert
366 may be substantially flat. Insert 366 may have an elongated
shape with one or more angled portions 376 on superior surface 378
of the insert.
As advancing element 368 is advanced, angled portions 376 may
engage extensions 450 of upper body 460. Advancement of advancing
element 394 and rotation of insert 366 may increase a separation
distance between upper body 460 and lower body 462.
FIG. 19B depicts a cross-sectional view of implant 360 before
expansion. During expansion, angled portions 376 on superior
surface 378 of insert 366 may engage angled portions 380 extending
downward from inferior surface 382 of upper body 362. As advancing
element 368 is advanced into recess 372 in lower body 364, insert
366 rotates in recess 372 on superior surface 370 of lower body
364. In some embodiments, insert 366 remains in recess 372 and is
not elevated during insertion and expansion of implant 360 in a
human spine. As insert 366 is rotated, angled portions 380 of upper
body 362 slide up the angled portions 376 of insert 366, and the
upper body is elevated above lower body 364 to increase a height of
implant 360 and/or to increase a separation distance between the
upper body and the lower body. The elongated nature of insert 366
may result in a more stable expanded implant than an insert of a
shorter length. As shown in FIG. 19B, angled portions 376 and/or
angled portions 380 do not include a platform portion. Thus,
implant 360 may have a variable expansion height. An expansion
height of implant 360 may be secured with advancing element 368 or
with a spacer of a desired height.
FIG. 19C depicts a view of an inferior side of upper body 362 with
insert 366 positioned on retaining post 384. Insert 366 may rotate
around retaining post 384. In certain embodiments, retaining post
384 may limit a height of implant 360 and/or limit a separation
distance between upper body 362 and lower body 364.
FIG. 20A depicts a perspective view of an embodiment of a c-shaped
expandable implant with a cam device. Implant 386 may include upper
body 388, lower body 390, insert 392, and advancing element 394. In
some embodiments, advancing element 394 may be an expansion member.
In some embodiments, insert 392 may be a cam. As with all of the
disclosed embodiments, the placement of implant 386 in the spine
will determine a shape of upper body 388 and lower body 390. In
some embodiments, lower body 390 may include recess 398 in superior
surface 396. In certain embodiments, insert 392 may be positioned
in recess 398.
In some embodiments, as shown in FIG. 20B, insert 392 may have a
generally cylindrical central portion 400 with opening 402 defined
therethrough. In certain embodiments, insert 392 may include one or
more projections 404 extending radially from central portion 400.
In some embodiments, projections 404 may be arms. Insert 392 may be
positioned in recess 398 in lower body 390 on a projection (not
shown) extending upward from a superior surface of the lower body
such that the projection fits in opening 402 of central portion 400
of the insert. The projection may align and/or retain insert 392 in
a desired position.
In some embodiments, upper body 388 may include one or more angled
portions or cam ramps 406 that extend downward from inferior
surface 408 of the upper body. In certain embodiments, cam ramps
406 may be positioned such that projections 404 of insert 392
engage the cam ramps as central portion 400 of the insert is
rotated around the projection of lower body 390, increasing a
separation distance between upper body 388 and lower body 390.
In certain embodiments, insert 392 may be rotated via the insertion
of advancing element 394 (e.g., a screw), as shown in FIG. 20C. In
some embodiments, stabilizers 412 may extend downward from inferior
surface 408 of upper body 388 or upward from a superior surface of
lower body 390. In some embodiments, stabilizers 412 may be, for
example, retaining pegs. Stabilizers 412 may be of various shapes
or sizes as required to limit separation of upper body 388 and
lower body 390 as desired. When upper body 388 is placed over lower
body 390, a large diameter portion (e.g., T-shaped, circular,
ellipsoidal, rectangular) of stabilizers 412 may be held in
openings 414 in lower body 390. In certain embodiments, stabilizers
412 may be inserted through inferior surface 416 of lower body 390
and then coupled (e.g., spot welded) to inferior surface 408 (e.g.,
openings in the inferior surface) of upper body 388.
As depicted in FIG. 20A, expansion of implant 386 may increase a
separation distance between upper body 388 and lower body 390 to
form gap 418 between the upper body and the lower body. The force
of advancing element 394 on projections 404 of insert 392 may
inhibit the insert from rotating after expansion, thus inhibiting
implant 386 from undesirably returning to an unexpanded position.
In some embodiments, a spacer may be placed in gap 418 between
upper body 388 and lower body 390 to remove the force on advancing
element 394 and to ensure that implant 386 remains in an expanded
position.
The cam device employed in the embodiment illustrated in FIGS.
20A-C, as with all the disclosed embodiments of expandable
implants, may also be employed in an articulating, or functional,
implant. FIG. 20D depicts a cross-sectional view of an embodiment
of an expandable, articulating implant with a cam insert. Insert
392 of implant 422 may be positioned in recess 398 of lower body
390. Projection 424 (e.g., a post) may extend upward from the
superior surface of lower body 390. Insert 392 may rotate about
projection 424.
Superior surface 426 of upper portion 432 of upper body 388 may
contact the bony surface of an adjacent vertebral body after
insertion. At least a portion of inferior surface 428 of upper
portion 432 may be concave. At least a portion of superior surface
430 of lower portion 434 may be convex. A convex portion of lower
portion 434 may be, for example, circular or ellipsoidal in shape.
In some embodiments, a circular convex portion may allow
biomechanical motion that mimics motion of the human spine. In
certain embodiments, an ellipsoidal convex portion may allow
translation as well as rotation between, for example; an upper
portion and a lower portion of an upper body of an implant. In some
embodiments, upper portion 432 and lower portion 434 of upper body
388 may articulate with respect to each other (e.g., may form a
functional joint). In certain embodiments, cam ramps 406 may extend
downward from inferior surface 436 of lower portion 434 into lower
body 390. Advancing element 394 may push against projections 404 of
insert 392, thereby rotating the insert and causing the projections
to engage cam ramps 406. As projections 404 of insert 392 engage
cam ramps 406 and the projections travel up the cam ramps, lower
portion 434 and upper portion 432 of upper body 388 may be elevated
with respect to lower body 390. As with the other disclosed
embodiments, stabilizers (e.g., captive pegs) may also be employed
to inhibit separation of upper body 388 from lower body 390.
After expansion of implant 422, gap 418 may exist between lower
portion 434 of upper body 388 and lower body 390. A spacer (e.g., a
shim) may be placed in gap 418 to inhibit implant 422 from
returning to an unexpanded position. A spacer may be of various
desirable shapes and/or sizes. For example, one side of a spacer
may be thicker than another side of the spacer to achieve a desired
lordotic angle of the implant. In some embodiments, implant 422 may
be inserted in a spine upside down (e.g., upper body 388 oriented
inferior to lower body 390) such that an axis of rotation of the
implant is located closer to the inferior body after insertion.
FIGS. 21A and 21B depict a perspective view of embodiments of
c-shaped expandable, articulating implant 422 depicted in FIG. 20D.
FIGS. 21A and 21B depict retention of stabilizers 412 in lower body
390. As shown in FIG. 21A, superior surface 426 of upper portion
432 of upper body 388 and inferior surface 416 of lower body 390
may include teeth 438. Teeth 438 may be of any regular or irregular
desired size, shape, and/or spacing to promote retention of implant
422 between vertebrae after insertion. In some embodiments, teeth
438 may be randomly spaced protrusions or barbs. In certain
embodiments, upper body 388 and/or lower body 390 may include
openings to allow for bone ingrowth into an interior portion of
implant 422.
FIG. 21A depicts implant 422 before expansion. In some embodiments,
no visible gap may exist between upper body 388 (or upper portion
432) and lower body 390 of implant 422. Thus, a height of implant
422 before expansion may be a minimal height of the implant (e.g.,
the implant may not be able to articulate before expansion). In
some embodiments, a visible gap may exist between upper body 388
(or upper portion 432) and lower body 390 of implant 422. Thus, a
separation distance between upper body 388 (or upper portion 432)
and lower body 390 of implant 422 may increase during expansion.
FIG. 21B depicts fully expanded implant 422 (teeth are not shown
for clarity) after advancement of advancing element 394. In some
embodiments, advancing element 394 may be a screw (e.g., a set
screw). In certain embodiments, advancing element 394 may be
positioned on a side (e.g., posterior side) of implant 422 (e.g.,
for a TLIF application). In certain embodiments, advancing element
394 may be positioned on an end of implant 422 (e.g., for a PLIF
application).
Implant 422 may be fully expanded when platform 440 of cam ramps
406 rests on a superior surface of insert 392 (e.g., on a superior
surface of projections 404 of the insert). In some embodiments,
articulation of upper portion 432 with lower portion 434 may be
determined by a degree of convex curvature of inferior surface 428
of upper portion 432 and superior surface 430 of lower portion 434
and/or a relative height (and depth) of complementary
convex/concave contacting surfaces of the upper portion and the
lower portion. In certain embodiments, stabilizers 442 may be used
to align upper portion 432 with lower portion 434 of upper body 388
and/or to retain the upper portion on the lower portion and/or to
limit articulation between the upper portion and the lower portion.
As depicted in FIG. 21B, stabilizers 442 may be coupled to lower
portion 434 of upper body 388 and reside in openings 444 of upper
portion 432. In some embodiments, stabilizers 442 may be coupled to
upper portion 432.
FIG. 22 depicts an embodiment of a portion of an expandable
implant. In the embodiment depicted in FIG. 22, insert 446 includes
four cam ramps 448. In other embodiments, an insert may include
fewer (e.g., 2 or 3) or more (e.g., 5 to 12 or more) cam ramps. In
contrast to the embodiment depicted in FIG. 21, in which the cam
ramps are a part of the upper body of the implant and are
stationary during expansion of the implant, cam ramps 448 may
rotate as advancing element 394 rotates insert 446. In some
embodiments, advancing element 394 may rotate insert 446 until an
inferior surface of extensions 450 of upper body 452 rest on a
superior surface (e.g., a platform) of cam ramps 448, as depicted
in FIG. 22. Thus, the portion of the insert depicted in FIG. 22 may
be used without a spacer to achieve a fixed separation distance
between an upper body and a lower body of an implant. In some
embodiments, a spacer may be used to provide extra stability and/or
to reduce force exerted on cam ramps 448 of insert 446. In certain
embodiments, a spacer may be used to achieve a separation distance
less than the fixed separation distance determined by a cumulative
height of cam ramps 448 and extensions 450 of upper body 452.
In some embodiments, one or more cam ramps may be positioned on an
inferior surface of an upper body or a superior surface of a lower
body of an implant. FIG. 23 depicts an embodiment of an upper body
of an implant. Upper body 464 may include cam ramps 406.
Advancement of an insert up a curved and/or inclined surface of cam
ramps 406 may determine an expansion height of an implant (e.g., a
separation distance between an upper body and a lower body of the
implant). Stabilizers 466 may allow upper body 464 and a lower body
of the implant to remain coupled during and after expansion of the
implant. In some embodiments, stabilizers 466 may limit a height of
an implant and/or a separation distance between an upper body and a
lower body of the implant. Opening 468 of upper body 464 may allow
bone graft material to be packed inside the implant.
In some embodiments, a spacer and an insert may include
complementary portions that allow a spacer to be coupled to an
implant (e.g., reversibly or irreversibly locked into place between
an upper body and a lower body of the implant). FIG. 24A depicts a
perspective view of an embodiment of spacer 470 coupled to insert
472. FIG. 24B depicts a perspective view of spacer 470. FIG. 24C
depicts a perspective view of another spacer 474. Spacers 470, 474
may include protrusion 476. In some embodiments, protrusion 476 of
spacers 470, 474 may be press fit or loose fit into a recess of a
member of an implant (e.g., an insert). Fitting (e.g., snapping)
protrusion 476 into a recess may advantageously provide a tactile
indication to a surgeon that spacer 470, 474 is properly placed and
secured in an implant.
Spacers may have various features designed to facilitate insertion
in an implant, retention in an implant, and/or removal from an
implant. For example, spacer 470 shown in FIG. 24B may include
recess 478. Recess 478 may allow spacer 470 to be grasped for
insertion in an implant and/or for removal from an implant. Spacer
474 shown in FIG. 24C may include lip 480. Lip 480 may facilitate
(e.g., guide) insertion of spacer 474 into a gap in an implant. In
some embodiments, lip 480 may promote retention of spacer 474 in a
gap between an upper body and a lower body of an implant. In some
embodiments, a spacer may include a lip around a superior and/or
inferior surface of the entire spacer. In certain embodiments, a
spacer may include a lip around a superior and/or inferior surface
of a portion (e.g., one side) of a spacer. In some embodiments, a
lip may be an external lip or an internal lip. In certain
embodiments, a lip on an inferior surface of an upper body or a
superior surface of a lower body of an implant may be used together
with or instead of a lip on a spacer.
FIG. 24D depicts a perspective view of an embodiment of an insert.
Insert 472 may include recess 482. Recess 482 may be complementary
to a protrusion of a spacer (e.g., protrusion 476 of spacers 470,
474). As depicted in FIG. 24A, protrusion 476 of spacer 470 may fit
securely in recess 482 of insert 472, inhibiting backout of the
spacer after the spacer has been fully inserted. FIG. 24E depicts a
perspective cross-sectional view of spacer 474 with lip 480 used to
maintain a separation distance between insert 472 and an upper body
of an implant.
FIG. 25 depicts a perspective view of an embodiment of an expanded
c-shaped implant during insertion of a spacer. Implant 484 may
include upper body 486 and lower body 488. Spacer 490 may be
inserted in gap 492 between upper body 486 and lower body 488.
Opening 494 in upper body 486 may allow bone graft material to be
packed inside implant 484.
FIG. 26A depicts a perspective view of an embodiment of an expanded
c-shaped articulating implant during insertion of a spacer. Implant
496 may include upper body 498 and lower body 500. Upper body 498
may include upper portion 502 and lower portion 504. Spacer 506 may
be inserted in gap 508 between lower body 500 and lower portion 504
of upper body 498. In some embodiments, stabilizers 510 may extend
from lower portion 504 through openings 512 in upper portion 502 of
upper body 498. A size and/or shape of stabilizers 510 and/or
openings 512 may allow a desired amount of articulation between
upper portion 502 and lower portion 504 of upper body 498 (e.g.,
about a convex portion of the superior surface of lower
portion).
FIGS. 26B and 26C depict perspective views of implant 496 after
spacer 506 has been fully inserted. FIG. 26B depicts implant 496
with upper portion 502 angled relative to lower portion 504 of
upper body 498. Superior surface of lower portion 504 may include a
convex portion (e.g., substantially ellipsoidal or round) that
articulates with a concave portion of inferior surface of upper
portion 502 to allow translation, rotation, anterior/posterior
bending, and/or lateral bending of upper portion 502 relative to
lower portion 504 of upper body 498, subject to size, shape, and
orientation of stabilizers 510 and openings 512. FIG. 26C depicts
implant 496, with details of stabilizers 510 and openings 512
visible. Stabilizers 510 may be shaped and oriented such that upper
portion 502 is angled onto lower portion 504 during assembly of
implant 496. Angled portions of stabilizers 510 and openings 512
may allow desired ranges of translational and/or rotational motion
of upper portion 502 relative to lower portion 504 while inhibiting
separation of the upper portion from the lower portion.
FIG. 27 depicts a perspective view of an embodiment of a c-shaped
expandable implant with a spacer. Implant 514 may include spacer
516 between upper body 518 and lower body 520. Spacer 516 may have
a larger profile than upper body 518 and lower body 520 of implant
514. Thus, a portion of spacer 516 may protrude from a
circumference of implant 514. A spacer with a larger profile than
an upper body and/or lower body of an implant may provide torsional
support and/or facilitate insertion of the spacer during a surgical
procedure.
FIG. 28A depicts a side view of an embodiment of a facet
replacement device. Facet replacement device 522 may include upper
pedicle screw 524 and lower pedicle screw 526. Rod 528 may be
retained in head 530 of upper pedicle screw 524 and head 532 of
lower pedicle screw 526. Rod 528 may have washer-type ends 534 that
allow for posterior compression, but not extension.
FIG. 28B depicts a side view of an embodiment of a facet
replacement device. Facet replacement device 536 may include rod
538. Rod 538 may include a single washer-type end 540 on lower end
542. Head 544 of upper pedicle screw 546 may have threaded locking
screw 548, as shown in the cross section in FIG. 28C. Threaded
locking screw 548 may hold rod 538 in place and inhibit head 544 of
pedicle screw 546 from swiveling while allowing rod 538 to rotate
and translate through the head of the pedicle screw.
FIG. 28D depicts a cross-sectional view of an embodiment of a
head-locking insert that may be used in conjunction with a pedicle
screw having a locking-type head. In some embodiments, insert 550
may have a similar shape to head 544 of pedicle screw 546. Insert
550 may be of solid construction, with opening 554 defined
therethrough. In some embodiments, opening 554 may substantially
align with the opening defined through head 544 of pedicle screw
546. As set screw 556 is engaged into head 544 of pedicle screw
546, force is applied to the top of insert 550 and is transferred
to the bottom of the head. The force locks head 544 of pedicle
screw 546, as with conventional locking pedicle screws; however,
the force is not transferred to rod 538. With no force transferred
to rod 538, the rod may rotate in and translate through head 544 of
the pedicle screw. Alternatively, a shorter insert 550 (e.g.,
threaded only part way into head 544) may be used to inhibit a
transfer of force to the bottom of the head such that the pedicle
screw head undergoes multi-axial motion while retaining the rod in
the head.
FIG. 29A depicts a side view of an embodiment of a facet
replacement device. Facet replacement device 558 may include upper
pedicle screw 560 and lower pedicle screw 562. Rod 564 may be
retained within heads of pedicle screws 560, 562. Both pedicle
screws 560, 562 may be secured with locking screws 566 that inhibit
heads 568, 570 of the pedicle screws from swiveling while allowing
rotation and/or translation of rod 564. Rod 564 may include rod
members 572, 574 coupled via ball joint 576. Ball joint 576 may
allow for a generally upward rotation, away from the bony surfaces
of the vertebrae to which pedicle screws 560, 562 are secured, but
inhibit a generally downward rotation, which would bring the ball
joint in contact with the vertebrae to which the pedicle screws are
secured.
FIGS. 29B and 29C depict side and top views, respectively, of an
embodiment of a facet replacement device. Facet replacement device
578 may include upper pedicle screw 580 and lower pedicle screw 582
having post-type heads 584, 586. Rather than the previously
described rod, retaining plate 588 may be included. Elongated
openings 590 may be defined through retaining plate 588 positioned
on the post-type heads 584, 586 of pedicle screws 580, 582.
Post-type heads 584, 586 may be allowed to move in elongated
openings 590, providing a limited range of motion. Employing
cushioning pads 592 made of rubber or other elastomeric
biocompatible material may dampen movement of retaining plate 588.
Post-type heads 584, 586 may also include threaded or lockable caps
594 to inhibit dislocation of retaining plate 588 from the
post-type heads.
FIG. 29D illustrates a pedicle screw having post-type head 584 used
in conjunction with a pedicle screw having a locking or non-locking
type head 598. Retaining plate 588 may be formed with rod 600 on
one end, which may be slidingly positioned through pedicle screw
head 598.
As shown in FIGS. 29E and 29F, post-type heads 604 of pedicle
screws 606 used in conjunction with retaining plate 588 may also
exhibit multi-axial motion. Post-type head 604 may be coupled to
pedicle screw 606 with ball joint 608. FIG. 29F shows spacer 610
disposed below retaining plate 588. Spacer 610 may allow for
rotation of ball joint 608.
FIG. 30 depicts facet replacement device 558 of FIG. 29A in place
on the spinal column. Note that implant 612 has been posteriorly
placed within the intervertebral space through the void created by
the surgical removal of the natural facet joint. In addition, ball
joint 576 may rotate in the posterior (upward) direction during
posterior compression to inhibit impact upon the bony surfaces of
the spine.
FIG. 31A depicts a perspective view of a portion of an embodiment
of a facet replacement device. Facet replacement device 614 may
include pedicle screw head 616, pedicle screw 618, lower saddle
620, upper saddle 622, and set screw 624. Rod 626 may be positioned
between lower saddle 620 and upper saddle 622. Set screw 624 may
secure lower saddle 620, upper saddle 622, and rod 626 in pedicle
screw head 616 of facet replacement device 614. In some
embodiments, a diameter of a portion of rod 626 held between lower
saddle 620 and upper saddle 622 may substantially the same diameter
as other portions of the rod. For example, rod 626 may be of
substantially constant diameter. In certain embodiments, a portion
of rod 626 held between lower saddle 620 and upper saddle 622 may
be reduced in diameter relative to other portions of the rod. FIG.
31B depicts a cross-sectional view of reduced diameter portion 628
of rod 626 positioned in pedicle screw head 616 of facet
replacement device 614.
FIGS. 31B and 31C depict perspective cross-sectional views of facet
replacement device 614. As shown in FIGS. 31B and 31C, rod 626 may
have reduced diameter portion 628 positioned between lower saddle
620 and upper saddle 622. Reduced diameter portion 628 of rod 626
may be secured in opening 630 formed by lower saddle 620 and upper
saddle 622. Rod 626 may be retained in a desired position between
lower saddle 620 and upper saddle 622 by O-rings 632. As depicted
in FIG. 31B, O-rings 632 may reside in grooves 634 in rod 626. A
position of grooves 634 in rod 626 may be chosen to allow
translation of the rod through opening 630 with O-rings 632
positioned in grooves 634. O-rings 632 may be made of any
biocompatible elastomeric material including, but not limited to,
silicone. Grooves 634 may have any desirable cross-sectional shape
including, but not limited to, rectangular, square, arcuate, or
v-shaped.
As depicted in FIGS. 31B and 31C, opening 630 formed by lower
saddle 620 and upper saddle 622 may have a diameter that exceeds a
diameter of the portion of rod 626 (e.g., reduced diameter portion
628 held between the upper saddle and the lower saddle. With a
diameter of opening 630 that exceeds a diameter of rod 626 held in
the opening, the rod may be able to move relative to pedicle screw
head 616 of facet replacement device 614. In some embodiments, rod
626 may be able to translate and/or rotate with respect to pedicle
screw head 616. In certain embodiments, rod 626 may be able to
rotate about axes parallel and/or perpendicular to a longitudinal
axis of the rod. As depicted in FIG. 31B, rotation of rod 626 about
an axis perpendicular to a longitudinal axis of the rod may result
in tilting or angulation of the rod relative to pedicle screw head
616. In some embodiments, movement of rod 626 in opening 630 may be
cushioned by O-rings 632.
FIG. 32 depicts a perspective view of a portion of an embodiment of
a facet replacement device that may be used in a 2-level spinal
stabilization procedure. Facet replacement device 636 may include
pedicle screw head 616, pedicle screw 618, lower saddle (not
shown), upper saddle 622, and set screw 624. Retainer 638 may hold
rod 626 in opening 630 formed by the lower saddle and upper saddle
622. Opening 630 may be sized as noted with respect to facet
replacement device 614 (FIG. 31) to allow rotational and/or
translational motion of rod 626 in the opening. O-ring 632 may
cushion movement of rod 626 in opening 630. Rod 626 used with facet
replacement device 636 may have a substantially uniform diameter.
That is, facet replacement device 636 does not require a portion of
rod 626 to have a reduced diameter. Therefore, pedicle screw head
616 may be placed at any desired position along a length of rod
626. Adjustable positioning of pedicle screw head 616 along a
length of a rod of uniform diameter may allow the use of the facet
replacement device 636 in a two-level or multi-level spinal
stabilization procedure.
Retainer 638 may be a c-shaped element with opening 640. A diameter
of rod 626 may exceed a length of opening 640. Thus, after retainer
638 has been snapped onto rod 626, the retainer may remain securely
on the rod. Rotational motion of rod 626 in opening 630 may be
limited by relative diameters of rod 626 and opening 630.
Translational motion of rod 626 through opening 630 may be limited
by placement of retainers 638 on either side of pedicle screw head
616.
FIG. 33A depicts a perspective view of an embodiment of a portion
of a facet replacement device including a plate rather than a rod.
Facet replacement device 642 may include pedicle screw 618, pedicle
screw head 644, and fastener 646. In some embodiments, fastener 646
may be, for example, a screw. Plate 648 may be coupled between
pedicle screw head 644 and fastener 646. In some embodiments, plate
648 may have a T-shaped cross section. In certain embodiments, a
T-shaped cross section may provide a lower profile than a rod,
advantageously requiring less space at a surgical site. Size,
thickness, and dimensions of a T-shaped cross section may vary as
needed for strength, stability, and surgical access. For example,
stem portion 650 of plate 648 may be of various heights.
FIG. 33B depicts a cross-sectional view of facet replacement device
642 including plate 648. Plate 648 may be coupled to pedicle screw
head 644 between lip 652 of the pedicle screw head and lip 654 of
fastener 646. In some embodiments, fastener 646 may have a threaded
portion that engages a threaded portion inside pedicle screw head
644 (threaded portions not shown). In some embodiments, spacer 656
may be positioned between pedicle screw head 644 and fastener 646.
In certain embodiments, spacer 656 may fit inside opening 658 in
plate 648 (e.g., between the plate and fastener 646). A diameter of
opening 658 may be sized such that plate 648 can rotate and/or
translate relative to pedicle screw head 644. In some embodiments,
spacer 656 may be a bushing or an O-ring. Spacer 656 may be made of
elastomeric materials such as, but not limited to, silicone. Spacer
656 may cushion and/or dampen movement of plate 648 relative to
pedicle screw head 644 and/or fastener 646 to allow smoother
biomechanical motion after insertion in a human spine.
FIG. 34A depicts a perspective view of an embodiment of a portion
of a facet replacement device with a pedicle screw that retains
mobility after a rod is secured. Facet replacement device 660 may
include pedicle screw head 662, pedicle screw 664, upper saddle
666, and set screw 624. Ball joint 668 of pedicle screw 664 may
rest in base 670 of pedicle screw head 662. A portion of rod 626
may contact ball joint 668 of pedicle screw 664. In some
embodiments, rod 626 may have a reduced diameter portion that
resides in pedicle screw head 662 and contacts ball joint 668 of
pedicle screw 664. In other embodiments, rod 626 may have a
substantially constant diameter.
In some embodiments, an outside portion of upper saddle 666 and an
inside portion of pedicle screw head 662 may be complementarily
threaded (not shown), such that the upper saddle may be threaded
into the head. In certain embodiments, pedicle screw head 662 may
be threaded such that upper saddle 666 may be threaded a limited
distance into the head (e.g., upper saddle 666 does not contact
base 670). Set screw 624 may inhibit backout of upper saddle 666
from pedicle screw head 662. A length of threading in pedicle screw
head 662 may be chosen such that upper saddle 666 may be fully
secured in the head without tightening rod 626 onto ball joint 668.
Thus, with rod 626 fully secured in head 662, the rod and pedicle
screw 664 both retain rotational mobility. In some embodiments,
O-rings 632 may be positioned on rod 626 on both sides of upper
saddle 666. Translation of rod 626 in pedicle screw head 662 may be
limited by the placement of O-rings 632 on the rod and/or by a
retainer.
FIGS. 34B and 34C depict cross-sectional views of facet replacement
device 660. As shown in FIGS. 34B and 34C, reduced diameter portion
628 of rod 626 may be held loosely between upper saddle 666 and
ball joint 668 of pedicle screw 664. With threading (not shown)
inside pedicle screw head 662 extending only partially down toward
the base of the pedicle screw head, upper saddle 666 may secure rod
626 in the pedicle screw head without causing the rod to bear down
on ball joint 668 of pedicle screw 664. With rod 626 and ball joint
668 able to move freely, the rod may retain rotational (and/or
translational) mobility after insertion of facet replacement device
660 in a human spine.
In some embodiments, instruments may be used to install elements of
an implant in a spine. Instruments may also be used to position
(e.g., rotate, translate, expand) elements of an implant in vivo.
In certain embodiments, a single instrument may be used to perform
multiple steps of a spinal procedure. For example, an instrument
may be used to position an implant in an intervertebral space and
to actuate an expansion member to expand the implant in the
intervertebral space.
FIG. 35 depicts instrument 700 for use in installing and expanding
an implant. Instrument 700 may have proximal end 702 and distal end
704. Instrument 700 may include outer shaft 706, driver 708,
holding device 710, and handle 712. As used herein, "shaft"
includes elongated members having various regular and irregular
cross-sections, including, but not limited to, round, square,
rectangular, hexagonal, or irregular. A shaft may be solid or
hollow.
Instrument 700 may include thumbwheel 714. Thumbwheel 714 may be
coupled to driver 708. Thumbwheel 714 may act as a control member
for driver 708. As used herein, "control member" includes any
element that is operable by a user to control position,
orientation, or motion of another element. Other examples of
control members include, but are not limited to, a knob, a lever,
or a button. In some embodiments, a control member may be operated
using a tool.
In one embodiment, thumbwheel 714 may be fixedly coupled to driver
708 such that driver 708 rotates as thumbwheel 714 is rotated. In
another embodiment, thumbwheel 714 may be threadably coupled to
driver 708 such that driver 708 translates along its axis when
thumbwheel 714 is rotated.
FIG. 36 depicts a detail view of distal end 704 of instrument 700.
Holding device 710 may hold an implant during insertion of the
implant between two vertebrae. As used herein, "holding device"
includes any element or combination of elements that may be used to
hold, support, or grip another element, such as an implant, spacer,
or insert. Examples of holding devices include, but are not limited
to, a clamp, a clip, or a threaded rod. In some embodiments, a
holding device may include one or more opposing holding elements.
For example, as shown in FIG. 36, holding device 710 may include
holding arms 716. Holding arms 716 may be hinged to base 718. Base
718 may be coupled to outer shaft 706. Holding arms 716 may be
coupled to spring clip 720. Spring clip 720 may maintain holding
arms 716 in a closed position (as shown in FIG. 36) unless at least
a predetermined amount of separation force is applied to instrument
700 and an implant.
Lobes 722 on holding arms 716 may engage complementary surfaces
(e.g., notches, grooves) on an implant or spacer. Engagement
between lobes and complementary surfaces on an implant or spacer
may promote engagement between an instrument and an implant or a
spacer. Holding arms may include other engaging elements, such as
tabs, grooves, or pins. In certain embodiments, the inner surfaces
of holding arms on a holding device may be flat. The inner surfaces
of holding arms may be textured or smooth.
In some embodiments, spring clip 720 may be at least partially made
of a shape memory alloy. Spring clip 720 may be actuated by
allowing the spring clip to reach a predetermined temperature. When
spring clip 720 is actuated, the spring clip may urge holding arms
716 outwardly from a closed position. In one embodiment, spring
clip 720 may be actuated by body heat. In another embodiment,
spring clip 720 may be actuated by electrical current carried by
insulated conductors in or on the instrument.
Base 718 of holding device 710 may allow for passage of driver 708.
Driver 708 may include inner shaft 724 and driver head 726. Inner
shaft 724 may be coupled with thumbwheel 714 (shown in FIG. 35).
Driver head 726 may have any of various forms suitable for
actuating (e.g., rotating, advancing) a portion of an expansion
member or insert. In one embodiment, a driver head may include
external threads that can engage internal threads on a portion of
an implant. Other examples of driver head types include, but are
not limited to, slotted, Phillips, square, hexagonal, or
hexalobular. In some embodiments, the driver head may engage a set
screw in the implant.
FIG. 37 depicts a detail view of proximal end 702 of instrument
700. Handle 712 may include grip portion 728 and end portion 730.
End portion 730 may include a surface suitable for receiving impact
by another instrument. Slot 732 may be provided between grip
portion 728 and end portion 730. Thumbwheel 714 may partially
reside in slot 732. In certain embodiments, surfaces of thumbwheel
714 may have knurls, ribs, or similar characteristics to facilitate
rotation of the thumbwheel.
Handle 712 may protect portions of the instrument from damage
during use. For example, handle 712 may protect against damage to
threads on inner shaft 724 when another instrument is used to
strike instrument 700. In one embodiment, a transverse cross
section of handle 712 at slot 732 may be generally rectangular, as
shown in FIG. 37. A rectangular cross section at slot 732 may allow
a user to access a sufficient portion of thumbwheel 714 to turn the
thumbwheel, but still protect thumbwheel 714 and inner shaft 724
(shown in FIG. 35) from damage. A transverse cross section of
handle at slot 732 may be shapes other than rectangular, such as
square, oval, hexagonal, or irregular.
Although the protecting portions of instrument 700 shown in FIG. 37
are an integral part of handle 712, a protector in other
embodiments may be a separate component from the handle. In certain
embodiments, a protector may be removable from an instrument so
that a user may access a driver and/or control member.
FIG. 38 depicts implant 484 held by instrument 700 after driver 708
has been operated to expand the implant. When implant 484 is
initially coupled to holding device 710, lobes 722 of holding arms
716 may engage in holding recesses 733 on either side of lower body
488. Engagement of lobes 722 in holding recesses 733 may help
maintain a position of the implant during insertion and/or
expansion of the implant. Engagement of lobes 722 within holding
recesses 733 may place implant 484 in a desired alignment for
insertion between the vertebrae and engagement with an expansion
tool. The location of holding recesses 733 may be selected
according to the approach to be used (e.g., TLIF, PLIF) and the
location of an expansion member of the implant. For example, for a
TLIF implant, holding recesses may, in some embodiments, be located
near both longitudinal ends of the implant.
In some embodiments, driver head 726 may engage an insert (e.g.,
insert 472 depicted in FIG. 24D) of an implant. In other
embodiments, driver head 726 may engage a set screw (e.g.,
advancing element 394 depicted in FIG. 21B) of an implant, which
may in turn actuate (e.g., translate or rotate) an insert.
Actuation of driver 708 may expand implant 484 to the expanded
position shown in FIG. 38. After implant 484 has been expanded,
instrument 700 may be pulled away from the surgical site with
enough force to overcome the closing force of holding device 710,
thereby spreading holding arms 716 apart to allow separation of
instrument 700 from implant 484 and removal of the instrument from
the site. In another embodiment, a release mechanism can be used to
spread holding arms 716 apart.
In some embodiments, an inserter for a spacer may be used in
combination with an implant holder and/or a driver for an expansion
member. In some embodiments, an inserter may include a guide that
engages a portion of an implant holder. The guide may be used to
position the spacer near a desired location near the implant and/or
to insert the spacer in the implant. Examples of guides include,
but are not limited to, a fork, a hook, a ring, a spring clip, a
tab, a rail, or a groove. In some embodiments, an inserter may be
used to guide a spacer to a location near an implant, such as at a
gap between an upper body and a lower body of the implant. In
certain embodiments, an inserter may be advanced on a shaft to
fully insert a spacer between upper and lower bodies of an
implant.
FIG. 39 depicts instrument 736 including inserter 738 for holding
spacer 470. Inserter 738 may include inserter shaft 740, inserter
handle portion 742, spacer holding device 744, and guide fork 746.
Guide fork 746 may engage outer shaft 706. Inserter handle portion
742 may include bend 748. Bend 748 may allow a proximal portion of
inserter handle portion 742 to be positioned close to handle 712 so
inserter handle portion 742 may be manipulated in a relatively
small incision.
In the embodiment shown in FIG. 39, inserter 738 may be easily
separated from outer shaft 706. Thus, the surgeon could first
insert and expand the implant, then introduce inserter 738 into the
incision. In other embodiments, an inserter may be permanently
coupled to the rest of an instrument.
FIG. 40 depicts a detail view of implant 484 held by instrument
736, as seen from the upper side of the implant. FIG. 41 depicts a
detail view of implant 484 held by instrument 736, as seen from the
lower side of the implant. In FIGS. 40 and 41, spacer 470 is
partially inserted between upper body 486 and lower body 488 of
implant 484.
In the embodiment shown in FIG. 40, spacer holding device 744
includes holding arms 716 that are fixed with respect to base 718.
Each of holding arms 716 may include ball detent mechanism 750.
FIG. 42 depicts a detail view of ball detent mechanisms 750. Detent
springs 752 may provide a desired amount of clamping force on
spacer 470. In other embodiments, a spacer holding device may
include hinged arms that are similar to those of holding device 710
shown in FIG. 36.
Referring again to FIG. 36, it is noted that spring clip 720 may
serve as a biasing element to maintain a holding force on the
implant. As used herein, a "biasing element" includes any element
that biases a member of a device toward one position. A biasing
element may be a separate element of a holding device or integral
to another element of the device (e.g., a holding arm). Biasing
elements include, but are not limited, resilient members such as
metal springs or elastomeric bands. Additional embodiments of
holding devices with biasing elements are described below.
FIG. 43 depicts holding device 710 including holding arms 716
hinged to base 718 and connected by coil spring 754. In one
embodiment, coil spring 754 is spot welded to the holding arms.
FIG. 44 depicts an alternate embodiment of holding device 710 that
includes spring arms 755. In certain embodiments, spring arms 755
may be made of 302, 314, or 316 stainless steel.
FIG. 45 depicts a holding device 710 having holding arms 716 made
of a shape memory alloy. Holding arms 716 may be actuated by
allowing the holding arms to reach a predetermined temperature.
When holding arms 716 are actuated, the holding arms 716 may move
outwardly from a closed position. Holding arms 716 may be actuated
using body heat, insulated electrical current, or another heat
source.
FIG. 46 depicts an alternate embodiment of a holding device.
Holding device 710 may engage a top surface of implant 484. Notches
756 in implant 484 may allow the outer surfaces of holding arms 716
to be flush with the outer surfaces of upper body 486 and lower
body 488, facilitating insertion of implant 484 between the
vertebrae. In another embodiment, a holding device may engage top
and bottom surfaces of a spacer for an expandable implant.
FIGS. 47A-47D depict a top view of an expandable implant during
expansion of the implant and insertion of a spacer between upper
and lower bodies of the implant. FIG. 47A depicts implant 484 on
instrument 700 before expansion of implant 484. Driver head 726 of
driver 708 may be advanced into a tapped through hole in lower body
488 of implant 484 until the tip of driver head 726 engages insert
472. Advancement of driver head 726 may rotate insert 472 to expand
implant 484 between the vertebrae (see FIG. 47B). Holding device
710 may exert sufficient force on implant 484 to maintain the
implant in a fixed position during actuation of driver 708.
Guide fork 746 of inserter 738 (shown in FIG. 39) may be placed on
outer shaft 706. Inserter 738 may be advanced on outer shaft 706 to
move spacer 470 into position between the upper body and the lower
body of implant 484 (FIG. 47C). Inserter 738 may be advanced until
spacer 470 is fully installed between the upper and lower bodies of
implant 484 (FIG. 47D). Once spacer 470 is fully installed,
instrument 700 and inserter 738 may be withdrawn from the surgical
site, either together or one at a time.
In certain embodiments, an instrument may include a movable element
for maintaining a holding device in a closed position. FIG. 48
depicts a distal end of instrument 758 including slide 760. Slide
760 may include projections 762. Projections 762 may define notches
764 at a distal end of slide 760. Bottom surfaces 766 of notches
764 may act as stops against axial motion of holding device 710.
Spring clip 720 may bias holding arms outwardly from the closed
position shown in FIG. 48. When projections 762 are adjacent to
holding arms 716 of holding device 710 (as shown in FIG. 48, for
example), the projections may inhibit outward rotation of the
holding arms, thereby keeping the holding device in a closed
position. When slide 760 is retracted from holding arms 716 (e.g.,
by moving the slide proximally with respect to the holding device),
the holding arms may move apart under the force of spring clip 720
to allow release of an implant from the instrument.
Other arrangements may be used to maintain a holding device in a
closed position. For example, a slide may include a cylindrical
sleeve that passes over the outer sides of a holding device. The
inner wall of the sleeve may inhibit the holding arms from moving
out of a closed position.
In some embodiments, a holding device for an implant or spacer may
be coupled to a control member, such as a thumbwheel or lever. The
control member may be operated to selectively hold and release the
implant or spacer. FIG. 49 depicts a perspective view of inserter
768 including holding device 710. Holding arms 716 of holding
device 710 may be coupled to coil spring 754 in a similar manner as
described above relative to FIG. 43. Coil spring 754 may bias
holding arms 716 into a closed position on a spacer. Cable 770 may
extend between thumbwheel 714 and holding arms 716 through hollow
shaft 772. Thumbwheel 714 may be operated to draw cable 770 away
from distal end 704 of instrument 768. Cable 770 may act against
the force of coil spring 754 to open holding arms 716, thereby
allowing the spacer to be released from the holding device.
Inserter 768 may include guide fork 746. Guide fork 746 may
slidably engage a portion of an implant holder (e.g., the outer
shaft shown in FIG. 35) to facilitate positioning of the spacer
prior to release of the spacer. In another embodiment, a control
member may be connected to a locking slide to selectively lock and
release a holding device.
FIGS. 50A and 50B depict instrument 774 including a pair of rods
for inserting implant 776 having spacer 778. Bottom rod 780 and top
rod 782 of instrument 774 may be commonly supported on base member
784. Bottom rod 780 may include threaded portion 781. Threaded
portion 781 may engage in a tapped hole in lower body 786 of
implant 776. In one embodiment, tab 787 on spacer 778 may engage a
channel or groove in top rod 782 to help guide and/or align spacer
778. Top rod 782 may be used to guide spacer 778 to a gap between
upper body 788 and lower body 786, as shown in FIG. 50A. Once
spacer 778 is in position for insertion between upper body 788 and
lower body 786 of implant 776, top rod 782 may be repositioned in
base member 784 such that a distal end of top rod 782 is behind
spacer 778, as shown in FIG. 50B. Top rod 782 can be used to
advance spacer 778 between upper body 788 and lower body 786. In
certain embodiments, top rod 782 may be used to impact spacer 778
between upper body 788 and lower body 786.
FIG. 51 depicts alternative embodiment of an instrument 790
including driver 708 with driver head 726. Driver head 726 may
include threaded portion 792. In one embodiment, threaded portion
792 may be threaded into a tapped through opening in an upper or
lower body of an implant. As threaded portion 792 of driver head
726 is advanced through the opening, a distal tip of driver head
726 may actuate (e.g., translate, rotate) an insert. Instrument 790
may include outer shaft 706 and holding device 710. In certain
embodiments, holding device 710 of instrument 790 may be shaped to
match a contour of an implant or a spacer. In one embodiment,
holding device 710 may have an arcuate shape. Driver head 726 may
be actuated by thumbwheel 714. Instrument 790 may include removable
cover 794. Removable cover 794 may protect thumbwheel 714 from
damage during use.
FIGS. 52A and 52B depict an alternate embodiment of an instrument
for placing and expanding an implant and inserting a spacer.
Instrument 796 may include base member 798. Base member 798 may
carry holder rod 800, driver rod 802, and inserter rod 804. Holder
rod 800 may threadably engage a tapped hole in lower body 786 to
support implant 806. Driver rod 802 may threadably engage through
hole 808 in lower body 786. Driver rod 802 may be advanced to
actuate insert 810 to increase a separation distance between lower
body 786 and upper body 788, thereby expanding implant 806. Spacer
812 may be threadably coupled to inserter rod 804. Inserter rod 804
may be guided on base member 798 to advance spacer 812 between
lower body 786 and upper body 788. Holder rod 800, driver rod 802,
and inserter rod 804 may be rotated to disengage the rods from
implant 806. The rods may be removable from base member 798. In
some embodiments, inserter rod 804 may be loaded into an open
channel in base member 798.
It will be understood that any or all of the threaded tips on rods
800, 802, and 804 may be replaced by other holding devices
including, but not limited to, the holding devices shown in FIGS.
36-44. It will be further understood that in other embodiments, an
instrument may omit one or more of the implant holder, the
expansion driver, or the spacer inserter. For example, an
instrument may include only an implant holder and an expansion
driver, or only an implant holder and a spacer inserter.
In an embodiments, a driver for components of a spinal system may
include a feature for locking with an element of a spinal system.
FIG. 53 depicts a schematic view of a proximal end of head 816 on
fastener 818 for a spinal system. Head 816 may include side hole
820. A fastener for a spinal system may include, but is not limited
to, a set screw, a pedicle screw, or a threaded top for a polyaxial
screw. FIG. 54 depicts a schematic view of a distal end of driver
822. Driver 822 may include sleeve 824 having socket 826. Driver
822 may include lock element 828. Lock element 828 may retractably
extend into socket 826. Button 830 on sleeve may be manually
operated to retract lock element 828 from socket 826. When sleeve
824 of driver 822 is placed on head 816 of fastener 818, lock
element 828 of driver 822 may engage in side hole 820.
Engagement of lock element 828 in side hole 820 may inhibit axial
separation of driver 822 from head 816 of fastener 818. A locking
element may reduce a risk of a fastener disengaging from a tool
during use. In certain embodiments, lock element 828 may be used to
capture a break-off head of a top for a polyaxial screw. In certain
embodiments, driver 822 may be coupled with a detachable handle. In
some embodiments, driver 822 may be used with a power tool (e.g., a
drill).
In an embodiment, an implant (e.g., for an expanse cage, dynamic
cage) may be placed in a human spine using a posterior approach to
a diseased lumbar disc. In some embodiments, the surgeon may use
the same approach as is typically used in a microdiscectomy, TLIF,
or minimally invasive posterior exposure. Such procedures involve
removing some of the lamina and the medial facet joint. More bone,
including the spinous process and the entire facet may be removed
if indicated.
The vital structures involved with the posterior approach are the
nerve roots. The exiting root is the root that leaves the spinal
canal just cephalad (above) the disc, and the traversing root
leaves the spinal canal just caudad (below) the disc. The thecal
sac houses the other nerve roots that exit lower. The triangle
between the exiting nerve root and the traversing nerve root
(Pambin's or Cambin's triangle) is the extent of the access to the
disc. The triangle may be enlarged by retracting the traversing
nerve root medially. If retraction is done too vigorously, however,
retraction injuries may occur and serious complications such as
nerve root sleeve tear may result, causing spinal fluid leakage,
nerve root injury, avulsion and even spinal cord injury.
After the lamina has been removed and the traversing root retracted
medially, the posterior annulus may be exposed. While the root is
retracted gently, the surgeon may create an annulotomy. Pituitary
forceps may be used to remove disc material. Successively larger
forceps may be used until an adequate amount of disc is removed.
Care should be taken not to penetrate the anterior annulus and
enter the retroperitoneal space. After adequate disc material has
been removed, the end plates may be prepared using osteotomes to
remove posterior ostephytes and cutting curettes to decorticate the
end plates. The object of end plate preparation is to remove the
cartilaginous tissue and score the cortical bone without completely
removing the cortical strength.
Once the end plates have been prepared, a trial may be placed in
the disc space. The trial should be snug without significantly
distracting the end plates. An unexpanded implant of approximately
the same size as the trial may then be inserted into the disc
space. Once positioned anterior to the nerve roots, the implant may
be expanded. In some embodiments, a spacer may be introduced
following expansion of the implant. The spacer may include a
protrusion, groove, or similar element that snaps or locks into
place to provide a tactile sensation as the spacer reaches a fully
inserted position. A tactile sensation may provide the surgeon with
positive feedback that the spacer is in place. In certain
embodiments, the implant may be further rotated within the space
after the spacer is introduced, according to the preference of the
surgeon.
An expandable implant (e.g., an expanse cage or dynamic device) may
allow a larger device to be placed into the disc from a posterior
approach without over distracting the nerve roots or the ligaments.
In some embodiments, the implant may be expanded without any over
distraction. This advantage may allow the surgeon to tension the
annulus, avoid resection of the anterior longitudinal ligament, and
decompress the nerve roots without requiring over distraction and
the attendant possibility of injury to the nerves and ligaments.
For reasons outlined above, many patients are not suitable
candidates for an anterior approach. In one embodiment, an implant
of less than about 12 mm in width is placed posteriorly without
over distraction. In another embodiment, an implant of less than
about 10 mm in width is placed posteriorly without
overdistraction.
In an embodiment, an expandable implant may expand throughout its
entire width. In some embodiments, an expandable implant may be
used for posterior disc height restoration without increasing
lordosis. In other embodiments, an expandable implant may be used
for posterior disc height restoration with increasing lordosis. In
certain embodiments, an implant may be placed using a TLIF
approach. Although some of the description herein relates to a PLIF
or TLIF approach, it will be understood that implants as described
herein may be placed using an anterior approach.
In this patent, certain U.S. patents, U.S. patent applications, and
other materials (e.g., articles) have been incorporated by
reference. The text of such U.S. patents, U.S. patent applications,
and other materials is, however, only incorporated by reference to
the extent that no conflict exists between such text and the other
statements and drawings set forth herein. In the event of such
conflict, then any such conflicting text in such incorporated by
reference U.S. patents, U.S. patent applications, and other
materials is specifically not incorporated by reference in this
patent.
Further modifications and alternative embodiments of various
aspects of the invention will be apparent to those skilled in the
art in view of this description. Accordingly, this description is
to be construed as illustrative only and is for the purpose of
teaching those skilled in the art the general manner of carrying
out the invention. It is to be understood that the forms of the
invention shown and described herein are to be taken as examples of
embodiments. Elements and materials may be substituted for those
illustrated and described herein, parts and processes may be
reversed, and certain features of the invention may be utilized
independently, all as would be apparent to one skilled in the art
after having the benefit of this description of the invention.
Changes may be made in the elements described herein without
departing from the spirit and scope of the invention as described
in the following claims.
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